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GH with NARODs for VHF-HI & UHF

360K views 579 replies 97 participants last post by  300ohm 
#1 · (Edited by Moderator)
Success !!! I got the Vhf-Hi gain going the right way with the colinear rod reflector models and with more gain to boot ! (This does not apply to the mesh models, for obvious reasons.)

Using the basic original SBGH gen1 colinear rod plans (with 10ga elements, 3/8 inch reflectors), I placed additional 28 inch, 3/8 inch reflectors 10 inches behind the 28 inch 10 ga NARODs that are 1/2 inch above the stubs. Oddly, using a larger reflector than the driven element, typical in most TV antenna designs, decreased performance, as did a smaller reflector.

The effective bandwidth for Vhf-Hi is somewhat limited to about 4 channels. I tweaked for channels 10 to 13, so if channels 7 to 9 are needed, adjustments have to be made.

The use of the NARODs levels out and dips the gain curve similiar to the SBGH JED Gold Standard model, so the original SBGH gen1 model is so far the best to use in this case so as to not exacerbate the dip further.

VHF-HI

CH Raw Gain SWR
-- -------- -----
07 5.56 dBi 62.3 (7.93 dBi at 180 degrees)
08 6.27 dBi 23.0 (8.02 dBi at 180 degrees)
09 8.07 dBi 5.67
10 9.66 dBi 2.37
11 9.81 dBi 3.7
12 9.26 dBi 3.58
13 8.66 dBi 3.16

Channel 10 pattern :



3D Picture :



UHF Raw Gain Chart :



UHF SWR :



NEC file :

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GW	146	3	0	-1.7322835	0	0	1.73228346	0	0.01
GS	0	0	0.0254		' All in in.
GE	0
EK
EX	0	146	2	0	1	0
GN	-1
FR	0	38	0	0	473	6
RP 0 1 10 1510 90. 0. 0. 20. 0. 0.
See development background in this thread: http://www.digitalhome.ca/forum/showthread.php?t=98619
 
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4
#366 ·
GH6 Side By Side

OK...I just finished my quick and dirty Double GH6 and basically I stacked 2 GH6's one above the other which seems to be how everyone is doing it.

That being said I am still considering putting this in my attic (this was NOT designed for outdoor use) and it might be too tall to fit. Yes I know I will lose signal but this is just a quick and dirty and I will be feeding 2 TV's that get little use.

My question is it seems everyone is building these stacked one on top of the other. Has any one put 2 GH6's side by side and connected them? If I can't fit my Double GH6 I am thinking I could easily cut it in half between the 2 antennas and have 2 GH6's standing next to each other about a foot apart and connect them that way.

Any issues with that? I would only do this if I have to or if this is actually better than having them one on top of the other...and I should know soon if there is room for them in the attic.
 
#367 ·
My question is it seems everyone is building these stacked one on top of the other. Has any one put 2 GH6's side by side and connected them?
Yes, mlord has. Stacking horizontally is much much harder to do successfully. And even done successfully, horizontal stacks have a bit less gain than vertical stacks. But there are other reasons to horizontally stack.

http://www.kyes.com/antenna/stackluge.html

And because of various reasons, stacked antennas in an attic sometimes perform worse than a single. Spacing distances in an attic would have to be determined by experimentation because there are way too many variables involved to do a meaningful model.

Commercial antennas, like the CM4228, DB8 or C4, are stacked horizontally more for box size considerations than for gain IMO.
 
#369 ·
hi lenl:

Been there, tried that. Was exactly like 300ohm said, performed worse than the single. Not GH6 models in this case, just two coat hanger/2x4 framed SBGHs side-by-side in the attic. When i disconnected the second one it improved considerably (checked the balun phasing both ways first to make sure that wasn't it). Using a single GH10 on my roof now with a tripod and 5 foot mast and having way better luck.
 
#371 ·
Attic Install

I tried to get the double GH6 in the attic and even banged up my head pretty good and it did not fit very well.

So I made two GH6's with narods out of the one unit. First I tried just one by itself and got this result:

The following channels were the only ones I could view solid: 50.1 (PBS), 63.1 and 68.1 (Spanish)

Other channels were coming in and breaking up: 2.1 (CBS), 4.1 (NBC), 7.1 (WABC),11.1 (PIX) and 31.1. I can not get 5.1 (FOX) or 9.1 (UPN) 2 major stations from NY at all.

Next I added the second GH6. Now in reading about combining 2 antennas the people talk in terms of 1/2 wave length or 1 wave lenght apart but what I need is how many inches apart. Anyway I put them next to each other in about the same orientation to the ESB and they are about 2 feet apart element to element. Then I ran about 4 feet of coax from each one's balun to a 2 to 1 splitter that I reversed and then ran the coax (about 30') to the TV.

The results showed much improvement:

I can now watch: 2.1, 7.1 11.1 31.1, 50.1, 63.1 and 68.1.

Other channels are breaking up: 4.1 and 5.1


I have ordere a CM7777 preamp to install. MY 2 outdoor antennas did not work very well until I put preamps on them. So the results in the attic with the dual GH6s is very very encouraging.

Bottom line is I think I am getting as good a result if not better than my out door antennas did when I tested them w/o preamps.

I suppose there is no guarantee that the preamp will be as effective in the attic. I also have to try to hook it up so it powers both GH6 antennas which will diminish I guess the results? I was thinking of connecting the preamp right after the splitter so it send the current up to both GH6's. If that does not work I can try using one GH6.

I will post results when I get the preamp. I went for a deal with a great price and free shipping but I have to wait a month to get it ($52.99).
 
#372 ·
New Build - need advice

This is my first post here but I've been hanging out for a couple of years.

After several successful experimental builds, each a significant improvement over the former, I want to build a more substantial antenna. I checked here to see what is new since my last build which added narods and narod reflectors to my DBGH6 (original-rev0).

Initially I am confused regarding which antenna is now best for me...you guys have been busy!

My real UHF channels are 19, 21, 25, 29, 30, 35, 40, 46 and 48. Local PBS stayed on VHF9. The added narods (and the sole reason for adding them) greatly improved VHF9 reception but still too many drop-outs so I built a 12ft yagi specifically for this channel. The yagi runs to TV via separate pre-amp and coax to an A/B switch at the TV. The yagi increased my viewable PBS reception time from 60% to 90%

My new "substantial" GH will keep the narods because I often receive VHF9 with it and usually, when I don't, I still receive the program guide which lets me know if I want to switch antennas.

Questions:

1. I think I want to build a DBGH6 rev2 w/narods but please let me know if a different design would better fit my needs, eg GH10 rev2 w/narods.

2. Presuming I build the DBGH6 rev2 a difference I see between rev0 and rev2 is the spacing of the elements. Original DBGH6(rev0), my current antenna w/narods, uses 44mm (1 3/4") spacing where as one plan for rev2 uses 86.9mm (3.42") but I've seen here mention of 85mm (3.35") and 89mm (3.5) spacings. What is the best element spacing for me to use? Does the feed gap remain at 2"?

3. Another issue is the feed point length which, for my plan of the DBGH6 rev2, is 35". Somewhere in this thread I think 300ohm said the 35" was optimized for CH 46. Further, one can optimize for other channels by making the feed points equal to wavelength x 2 - 2%. My available mid-range UFH is around CH 35, 590MHz+/-, 1.667ft wavelength. Should I increase the 35" feed points to 39.21" for my mid-range 1.667 wavelength?

Thank you in advance for any light you can shed on these issues. I complement all you experts for the fine job you do on this forum. Your dedication is remarkable!
 
#373 ·
Post your TVFool image, so we can see your situation a little better.

2. Presuming I build the DBGH6 rev2 a difference I see between rev0 and rev2 is the spacing of the elements. Original DBGH6(rev0), my current antenna w/narods, uses 44mm (1 3/4") spacing where as one plan for rev2 uses 86.9mm (3.42") but I've seen here mention of 85mm (3.35") and 89mm (3.5) spacings. What is the best element spacing for me to use?
The sweet spot spacing for the DBGH6(rev0) was determined to be between 85m and 105mm instead of 44mm. I use 89mm because thats the distance across my tees, which makes a nice resting place for the elements.
 
#374 · (Edited by Moderator)
New Build - need advice

Thanks for the quick reply 300ohm.

I'm going to try to post TV fool and a couple of pics of my present build but I've never worked w/photobucket so bear with me.

Here' TV fool. Disregard any stations to the north. Mountain top in the way. Also ignore stations to WSW...trees. I just get the stations (some) pointing the antenna to the south +/-



This is pic of current DBGH rev0 w/Narods. Clickable thumbnails.



And pic of DBGH & Yagi temp set at shop; 100ft (wire length) from TV. Much better reception here that at house (tree shadow at house)

 
#375 ·
Element Crossover of DBGH?

One question regarding tying the elements together on a DBGH. On an 8 bay antenna like the MCLAPP the elements crossover on each side of the 8 bay.

On the gh6 if you put a double together stacked one GH6 above the other are the element wires supposed to be crossed over at all before the connection point? Or is that a no-no on the GH6?

Hopefully my question is coherent. The pictures I have seen seem to say the answer is no crossover. Must be a bad thing for the DBGH.
 
#377 ·
Local PBS stayed on VHF9. The added narods (and the sole reason for adding them) greatly improved VHF9 reception but still too many drop-outs
OK, channel 9 is at -8 NM so no surprise there, except that you get it at all, heh.
The NARODs do subtract a bit of UHF gain across the board, so if you dont need them, remove them.

Somewhere in this thread I think 300ohm said the 35" was optimized for CH 46. Further, one can optimize for other channels by making the feed points equal to wavelength x 2 - 2%. My available mid-range UFH is around CH 35, 590MHz+/-, 1.667ft wavelength. Should I increase the 35" feed points to 39.21" for my mid-range 1.667 wavelength?
Yeah, you could. It depends on which channels are more valuable to you.
 
#378 ·
New Build - need advice

I guess this site does not allow thumbnail photos. I'll post larger ones in the future.

Thanks 300ohm

OK, channel 9 is at -8 NM so no surprise there, except that you get it at all, heh.
The channel 9 I am referring to is near the top of the list, virtual 6.1, real 9, w/7.9 NM. It broadcasts on 189MHz. It is the only VHF channel I am interested in (but 10.1 may also be VHF...I get signal at about the same strength with DBGH and yagi).

Adding narods (the VHF mid-range model) to my DBGH allowed me to view VHF 9 occasionally but reliability was low. I'd receive it most of the time but without enough signal strength to create the picture. It is very aggravating to loose signal in mid program so I built the FM yagi.

My results trying to get VHF 9 (percentages equal percent of time I could watch when I wanted; mostly evenings):
XG91 - rarely - 5%
DBGH - rarely - 10%-15%
DBGH w/narods - 40%-50%
Above moved to better location - 60%
yagi - 90%-95%

The NARODs do subtract a bit of UHF gain across the bpard, so if you dont need them, remove them.
Is there an estimate loss of UHF gain?

Post yagi I still appreciate the narods because I can get the PBS (above channel) program guide even when signal is too low for a picture. If I see something I want to watch but not enough signal w/DBGH I switch antennas. A splitter/combiner would solve this issue and I could get rid of the narods. I connected the yagi with separate pre-amp/coax/AB switch instead of a splitter at the antennas because I thought I'd get less loss. If this is not the case can you recommend a good low-loss splitter?

Yeah, you could. It depends on which channels are more valuable to you.
UHF virtual channels 3.1, 13.1, 40.1, 10.1 and 58.1 are most important, in that order, and spread across much of the UHF spectrum. This leads me to believe optimizing feed point for mid UHF would be wise. Is my math correct for the separation of the bays?

I've also wondered about using top-hat narods to get rid of the mid-range dip. On the top-hat forum you suggested that top hats could be added to a DBGH although it does not seem that anyone has reported on the outcome of this. You gave dimensions for the top hats and said bay separation and feed points would need adjusting but did not mention the latter dimensions. Would my proposed separation for mid-range UHF work?

If a good low-loss splitter is available (ie no more loss than my Winegard TV-0151 AB switch) then maybe my best bet is a DBGH without narods.

If you were me which GH model would you build? Could you post a link to that design or the NEC2 code so I make sure I build the right one? There are so many to choose from and I am not always sure exactly which revision or design is being referenced in discussions.

I should also mention my difficult site. Distance to antenna farm puts me at deep fringe but I also live in the mountains with a couple of ridges just above my LOS plus lots of trees. I have heard that TV Fool accounts for topography but I have my suspicions since it shows I should receive stations to the NNW but clearly have a couple substantial ridges in the way.

Thanks for all your research and the attention you give to us DIYers.
 
#379 ·
Is there an estimate loss of UHF gain?
It depends on the channel, but around .5 dbi and you could use every bit of gain.
I connected the yagi with separate pre-amp/coax/AB switch instead of a splitter at the antennas because I thought I'd get less loss.
Yeah, thats a good way. You could use a preamp that has separate uhf and vhf inputs just fine too (without NARODs).
Ideally a CM0264 like mine with 300 ohm inputs, but they now seem unavailable.
You gave dimensions for the top hats and said bay separation and feed points would need adjusting but did not mention the latter dimensions. Would my proposed separation for mid-range UHF work?
Yes, that would give you enough room.



I should also mention my difficult site. Distance to antenna farm puts me at deep fringe but I also live in the mountains with a couple of ridges just above my LOS plus lots of trees.
Generally, in mountainous situations, aim for the mountain peaks.
If you were me which GH model would you build?
Basically, what you have now looks pretty good. Since you got channel 9 covered with the yagi, I would take off the NARODs. To simplify things, I would use a preamp with separate uhf and vhf inputs (the vhf antenna can be in a different direction than the uhf antenna) Which make and model preamps are you using now ?
 
#380 ·
New Build - need advice

It depends on the channel, but around .5 dbi and you could use every bit of gain.
I sure can. That's been my goal...max gain, min loss.

Yeah, thats a good way. You could use a preamp that has separate uhf and vhf inputs just fine too (without NARODs).
Ideally a CM0264 like mine with 300 ohm inputs, but they now seem unavailable.
Which make and model preamps are you using now ?
I tried to find a CM0264 when you recommended it in another forum some time ago. No luck for me either trying to find one. Are you saying that if I could find a double input VHF/UHF preamp with as good of specs as my separate Winegard AP-8275's I would use the double input preamp as the combiner and thereby cut the loss that either a combiner or my current AB switch induces?

Generally, in mountainous situations, aim for the mountain peaks.
The ridges are way far away and obscured by a forest of trees; I can't see the ridges. With great difficulty I attempted to draw a line between the towers and my antenna referencing Google Earth. Best I could tell is that they are just above my LOS so I just tilt my antennas up a little from vertical; about 3 degrees more or less. Reception of some channels, like 3.1 (35 real), are greatly improved with antenna tilt but if I tilt for max reception on 3.1 others often fade so it has been a trial and error process to find a semi-sweet compromise spot.

Which make and model preamps are you using now ?
Each antennas uses a Winegard AP-8275. This was the highest gain, lowest loss preamp I could find/afford. It is an 82 channel preamp and I understand it is good for VHF as well as UHF. Alas there is only one input so I have used a separate preamp for each antenna.

Basically, what you have now looks pretty good. Since you got channel 9 covered with the yagi, I would take off the NARODs.
The object of the new build is to construct a more robust assembly for winter and snow and in the process see if I can grab a bit more gain on the way. Since I have the Gen 0 DBGH6 (I think...with the 1 3/4" feed gap) shouldn't I build the 89mm+/- feed gap design ? I believe that would be your design for post #20 of this thread.


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GW	166	25	-4.1338583	-0.3937008	42.5	-4.1338583	-12.440945	42.5	0.1875
GW	167	25	-4.1338583	0.39370079	32.5	-4.1338583	12.007874	32.5	0.1875
GW	168	25	-4.1338583	-0.3937008	32.5	-4.1338583	-12.007874	32.5	0.1875
GW	169	25	-4.1338583	0.39370079	27.5	-4.1338583	12.4409449	27.5	0.1875
GW	170	25	-4.1338583	-0.3937008	27.5	-4.1338583	-12.440945	27.5	0.1875
GW	171	13	0	6.73228346	50	0	12.3228346	50	0.05094856
GW	172	13	0	-6.7322835	50	0	-12.322835	50	0.05094856
GW	173	13	0	6.73228346	20	0	12.3228346	20	0.05094856
GW	174	13	0	-6.7322835	20	0	-12.322835	20	0.05094856
GW	175	13	0	-15.125	50.5	0	0	50.5	0.0511811
GW	176	13	0	0	50.5	0	15.125	50.5	0.0511811
GW	177	13	0	-15.125	19.5	0	0	19.5	0.0511811
GW	178	13	0	0	19.5	0	15.125	19.5	0.0511811
GW	179	25	-11.5	15.125	50.5	-11.5	-15.125	50.5	0.1875
GW	180	25	-11.5	15.125	19.5	-11.5	-15.125	19.5	0.1875
GW	181	15	1	-1	35	1	-1	17.5	0.05094856
GW	182	15	1	1	35	1	1	17.5	0.05094856
GW	183	15	1	-1	0	1	-1	17.5	0.05094856
GW	184	15	1	1	0	1	1	17.5	0.05094856
GW	185	3	1	-1	17.5	1	1	17.5	0.05094856
GW	186	1	0	1.73228346	35	1	1	35	0.05094856
GW	187	1	0	-1.7322835	35	1	-1	35	0.05094856
GW	188	1	0	-1.7322835	0	1	-1	0	0.05094856
GW	189	1	0	1.73228346	0	1	1	0	0.05094856
GS	0	0	0.0254		' All in in.
GE	0
EK
EX	0	185	2	0	1	0
GN	-1
FR	0	38	0	0	473	6
RP 0 1 10 1510 90. 0. 0. 20. 0. 0.
To this design I'd leave off the Narods and Narod reflectors and increase my feed point length from 35" to 39 3/16" per my observation above.

My original build has elements, reflectors and narods all from 9ga galv wire. On new build I hope to use 6ga copper for driven elements, 10ga copper for feed lines and 3/8" dia aluminum for reflectors. My hope is that this upgrade along with the two mods in the paragraph above may yield and additional bit of gain.

An additional improvement will be spacing the DBGH off the mast at least 3/4" as I understand this too is beneficial.

Please confirm I'm on the right track here. Thanks for all your help!
 
#381 ·
Are you saying that if I could find a double input VHF/UHF preamp with as good of specs as my separate Winegard AP-8275's I would use the double input preamp as the combiner and thereby cut the loss that either a combiner or my current AB switch induces?
It would simplify things and save the loss from the combiner. The AB switch doesnt really produce a loss, except insertion loss. Since you already have good quality high gain preamps, I would keep what you have.
Reception of some channels, like 3.1 (35 real), are greatly improved with antenna tilt but if I tilt for max reception on 3.1 others often fade so it has been a trial and error process to find a semi-sweet compromise spot.
Yeah, I see what youre saying. Its liable to be that way for each channel. There are remote antenna tilters, but I dont know if youre willing to go to that expense.

Since I have the Gen 0 DBGH6 (I think...with the 1 3/4" feed gap) shouldn't I build the 89mm+/- feed gap design ? I believe that would be your design for post #20 of this thread.
Yep, thats what I use and its very good, durable against the wind and pretty easy build for a 17 dbi antenna, and not excessively large.
A DBGH made from JEDs SBGH10 would in theory have higher gain, but its going to be much larger and a much more complicated build.
On new build I hope to use 6ga copper for driven elements, 10ga copper for feed lines and 3/8" dia aluminum for reflectors. My hope is that this upgrade along with the two mods in the paragraph above may yield and additional bit of gain.
Yes, youre on the right track. 5" long grey plastic UV resistant gutter ferrules are available at ACE Hardware for about 15 cents apiece. They fit 3/8" tubing perfectly for the colinear reflector rods.

A 3/8" fiberglass perch at the very top of the antenna can help to eliminate bird problems.
 
#382 · (Edited by Moderator)
New Build - need advice

300ohm you are a gem!

You've helped tremendously getting my ducks in a row for this next build. I'm so satisfied with my current build having been lucky enough to continually increase my reception at each upgrade I did not want to blow it now when building my "final" version.

I'm going to search tomorrow for local supplies and the gutter ferrules were already on the list; there are two ACE Hdwre stores in town. Last night I web checked Metal Supermarket and found that solid AL rod was much cheaper than AL tubing. We have a pretty good metal supplier nearby so I'll see first what they've got.
 
#383 ·
Quote:
Local PBS stayed on VHF9. The added narods (and the sole reason for adding them) greatly improved VHF9 reception but still too many drop-outs
OK, channel 9 is at -8 NM so no surprise there, except that you get it at all, heh.
Unfortunately I'll need a 12ft length to upgrade my yagi.
Actually, because of the very low NM comparison, its one of the best real life examples that does show that the DBGH with NARODs and NAROD reflectors is getting about the 10 to 11 dbi vhf-hi gain as modeled. I estimate that a 12 ft channel 9 yagi gets about 14+ dbi.
 
#385 ·
Disappointed w/new build

Actually, because of the very low NM comparison, its one of the best real life examples that does show that the DBGH with NARODs and NAROD reflectors is getting about the 10 to 11 dbi vhf-hi gain as modeled. I estimate that a 12 ft channel 9 yagi gets about 14+ dbi.
The program that modeled the 12ft channel 9 yagi estimated the gain at 11.8dBd.

What's the difference between "dbi" and "dBd"?

Without ability to measure gain I don't know how the DBGH w/narods compare numerically with the yagi. A generalization of my results are DBGH without narods received CH9 at 2-6 signal strength, with narods at 28-35 signal strength and the yagi at 50-70 signal strength.

But I'm really writing this post because of my disappointment with the results of my new build. This is the first time my "upgrade" efforts has reduced performance. I seem to be getting about 20% less signal with my new model. I had hoped for 5% to 15% better signal.

Per discussion above I replaced my lightweight experimental (original) DBGH6 w/narods with a heavier model DBGH6.

Here are the differences:
Spread director element spacing from 1 3/4" to 3 3/4" per current recommendation (3 3/4" = middle of 85mm-105mm "optimum")
Spread director/reflector spacing from 3 15/16" to 4 1/8" per current recommendation
Spread feed gap from 13/16" to 2" per current recommendation
Spread bay separation from 5" to 9 3/16" to optimize for mid-range UHF 590MHz
Spread feed point from 35" to 39 3/16" to optimize for mid-range UHF 590MHz
Upgraded directors from 13ga galv wire to 6ga copper
Upgraded feed wires from 13ga galv wire to 10ga copper
Upgraded reflectors from 9ga galv wire to 3/8" solid aluminum
Built to tighter tolerances; more accurate construction

Here is my plan:
http://i925.photobucket.com/albums/ad100/rayw3/Antenna/Antenna%20DBGH%20no%20Narods%20Mid%20UHF/rwDBGH_MidUHF_092710.jpg

And a couple of photos:



http://i925.photobucket.com/albums/ad100/rayw3/Antenna/Antenna DBGH no Narods Mid UHF/IMG_3818.jpg

http://i925.photobucket.com/albums/ad100/rayw3/Antenna/Antenna DBGH no Narods Mid UHF/IMG_3810.jpg

So what went wrong??? Removing narods, upgrading materials, and changing spacings to current recommendations should have all contributed an increased UHF signal strength and yet it is less. Did I goof by spreading the bays and feed point?
 
#386 ·
Looks like a very nice job, you should be proud.

The program that modeled the 12ft channel 9 yagi estimated the gain at 11.8dBd.

What's the difference between "dbi" and "dBd"?
dBi is the forward gain of an antenna compared with the hypothetical isotropic antenna, which uniformly distributes energy in all directions.
dBd is gain over a reference dipole, which has a gain of 2.15 dBi. Therefore, dBi is dBd plus 2.15, which is 11.8 plus 2.15 = 13.95 dBi in this case.

Did I goof by spreading the bays and feed point?
I dont think so. Are you using the same balun to compare with and even if it is or isnt, are you sure its not damaged ?

The antenna hasnt been modeled with your old combination of spacing and galvanized materials. There is an off chance that you had hit upon a good combination for your particular area. However, the odds of that happening is like successfully navigating an asteroid field, which are approximately three thousand, seven hundred and twenty to one. :p
 
#387 · (Edited)
Disappointed w/new build

Thank you for the dBi/dBd explanation.

Are you using the same balun...?
Yes, it is the same balun and same preamp. One difference is old antenna used 300ohm flat wire from feed wires to balun and new build uses two (separate) 14ga stranded copper wires. Maybe there is a problem with this? Could reversing the wires on balun create a difference in reception; ie is there a polarity it the way the feed connects to the balun?

The antenna hasnt been modeled with your old combination of spacing and galvanized materials.
Odd. I just assumed the original configuration (spacing) had indeed been modeled (but naturally not my individual materials) and that model was used to compare the various refinements that have since been made. I believe the dimensions I used were from the "original", revision 0, DBGH6. I had found that plan last year on the web prior to finding this site.

Reception with the new build improved as the day progressed and during the evening so perhaps I was experiencing a "lull" when I first hooked it up. A lull is not an uncommon event in that I am located so far from the towers, in a forest, and slightly below a ridge. So many things seem to affect signal strength, ie wind, heat, cool, evening twilight (or so it seems). Never the less I still feel I'm somewhat below par compared with the old design.

Antenna elevation with the new build is a couple/few feet different due to the change from rectangle to single pole support structure and also the spreading of the bays. Tomorrow I'll play a bit with elevation and tilt and see if by chance my new location is a bit outside the sweet spot.

Good to hear you don't think I goofed with the bay spreading and increased feed point. I was not looking forward to cutting the pole shorter as I'd compromise the strength of the full length dowel glued in the Sked 80 conduit.

I was pleased with the build itself though it took somewhat longer than anticipated. I had to re-do the triangles with the heavier plexi you see in the photo and do the lashing. I first used 1/8" plexi triangles but I could not tighten them down enough to keep the directors rigid. I had flattened the T's expecting to create a support surface but it turned out it was not wide enough to do the job. Of course after the fittings were glued I could not add a wider support as it would have elevated the directors. Instead I made the heavier triangles and lashed the directors to the triangles. This created a very rigid attachment. I lashed with marine grade waxed polyester whipping twine. I have used this on dock lines in the weather for several years without visible degradation so it seems reasonably UV resistant. Time will tell if it is up to the task for the antenna. Note the chamfered holes and eased edges of the plexi to reduce sharp edges.

Another variation I did was lash a 1/8" diameter wood dowel spacer at the ends of the reflectors. I liked the gutter ferrules but was not completely satisfied with the rigidity. The spacer rod does little to hold the reflectors in plane (too flimsy) but does wonders maintaining spacing as the entire group now acts as a unit and individual reflectors cannot droop. A better choice for the spacer may be a 1/4" fiberglass rod and I'll look into this if I get this antenna to receive at least as good as my previous model. I think possibilities for materials may be a chimney sweep pole or a wire fish pole (used for pulling electrical wire through stud walls). A heavier rod would help holding reflector alignment in plane but still small enough to keep windage down.

I had a bit of trouble getting the feed wires exactly as I had wished. In the end one of the 45 degree legs was a tad long and maintaining the 2" feed gap caused the long leg to lay flatter and the opposite one to lie steeper while maintaining the 1" offset from the elements. To compensate I bowed the long leg slightly to effectively shorten it so I could keep the rest of the geometry correct. Also I could not bend the feed wire legs to solder exactly on the apex of the element bend. They are likely 1/4" behind the apex. I'd disassemble and re-do if you think this could help.
 
#389 · (Edited by Moderator)
Pac C said:
Another variation I did was lash a 1/8" diameter wood dowel spacer at the ends of the reflectors. I liked the gutter ferrules but was not completely satisfied with the rigidity. The spacer rod does little to hold the reflectors in plane (too flimsy) but does wonders maintaining spacing as the entire group now acts as a unit and individual reflectors cannot droop. A better choice for the spacer may be a 1/4" fiberglass rod and I'll look into this
There are cheap 1/4 and 3/8 ths and other sizes of fiberglass rods {used for electric fences} -- I found for wide reflector center spacing they provide a lot of stiffness thru the center of the mast ! the mast material compresses the gutter ferrules tight onto the fiberglass too. If you use two, one on each side you don't loosen the 'grip' on the alu tubes . . .
 
#390 · (Edited by Moderator)
Disappointed w/new build

Could you post a good pic of the balun connection ?
I'm new to photobucket and this forum's 600 pixel wide limit. The attached photos show the balun connection and the feed connection. I had to brighten up the photos a lot because the bright sky contrast overexposed the originals. If these do not show what you want let me know and I'll try to redo them






I had company all day but now they are gone so now I'm going out to experiment with elevation and tilt.
 
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