[IDRick]

I'm interested in comparing several antennas and wanted to include a representative version of the GH. There's so many versions published on this site that I don't have a clue which to use... My test situations are relatively easy and do not require a top shelf antenna. But, IMO, it's always good science to use postive and negative controls. I do my testing at my home and at my son's home. TVFool's are shown below.

My home: http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id=8d17f3dbfec0d8
My son's: http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id=8d174770daa696

All my previous efforts have been with M4's and M2's (outstanding antennas in my book!) and I consider the M4 to my "gold standard". As I recall the modeling data, M4's and GH's are very similar in gain so maybe it's not worth the effort to have two "positive controls". Anyway, I'd like to try building a GH that is travelworthy (my son lives 270 miles away) and if possible, use the same reflector as the M4 (36" by 36" 1x2 screen). The size of the reflector is what makes it difficult to transport multiple antennas... There are high VHF and UHF stations at both test locations so I guess Narods are required for the GH, right? Any thoughts/recommendations on which one to build and any plans?

Thanks!

 

[300ohm]

I'd like to try building a GH that is travelworthy (my son lives 270 miles away) and if possible, use the same reflector as the M4 (36" by 36" 1x2 screen). The size of the reflector is what makes it difficult to transport multiple antennas... There are high VHF and UHF stations at both test locations so I guess Narods are required for the GH, right? Any thoughts/recommendations on which one to build and any plans?

The NAROD models are, for obvious reasons, all colinear rod reflector models, which can be built to fold up for travel purposes.

RE: your sons location.
Those signals are so strong I dont think you can get any type of meaningful comparison readings. They are also so strong that you really dont need the NARODs for the vhf-hi channels.

RE: your location.
For all practical purposes, you only need NARODs for vhf-hi channel 13. Channel 8 is so strong that it should come in without NARODs.
For your situation, I would build a reflector-less SBGH with NARODs. Granted it has less gain than a M4, but looks to be more appropriate for your situation because its bidirectional.

Why do you have a reflector on your M4 anyway ?

 

[IDRick]

Hi 300 ohm,

Way back when I started with a DIY antenna, you and mclapp (in a different forum) recommended the 10x9.5 M4 for my situation due to the 70 degree spread between channels in the SW and W direction. This was before NARODs were invented so the M4 also had better VHF reception than a GH. All the stations to the NE of my home are a repeat of channels to the SW/W. My everyday M4 is mounted in the attic with measured penetration losses of 6-8 dB to the West and 12-14 dB to the SW. My stations to the west lose another 3 to 4 dB due to aiming 45 degrees off axis and my distribution losses total 11 to 13 dB. Getting the additional 3 to 4 dB's with the reflector seemed appropriate plus I use a pre-amp to cover distribution losses. Very rock solid performance and no overload. All channels to the NE are blocked by the chimney.

I do my antenna comparisons by measuring margin to dropout. Antenna A with 3 dB more gain will have ~3 dB higher margin to dropout than Antenna B. NM is not overly important as long as I can receive the station and it is not too strong to overload the tuner. My son's location has more high vhf channels than mine so I like to do tests at his place and it's a good father/son activity! I should also state I'm not testing fringe antennas but want a good high gain antenna to relatively place the test antenna versus others. Just a hobby... After thinking about this a little, the Winegard 7694 is probably a better bet for a positive VHF control than either the M4 or GH. But the 7694 is not very portable... Thanks for taking a look and giving advice.

 

[300ohm]

My son's location has more high vhf channels than mine so I like to do tests at his place and it's a good father/son activity!

He's got channels 7, 9, 10, 13 all at over 58.9 NM. Thats incredibly strong. Im pretty sure he could get those without NARODs.

But if you want a NAROD model, I would choose a lower gain one from here :

http://clients.teksavvy.com/~nickm/gh_n_uV.html

Too much gain, like the Winegard 7694 or the GHn3 models is probably going to cause more problems for him than it would solve.

He would probably do great with a reflectorless SBGH (the easiest to build) or even a reflectorless M4, and theres no transportation problem with those, heh. And when mounted outside, practically no wind resistance.

 

[IDRick]

Yes, you correct. We can get a clear signal with bare coax laying on the roof! However, margin to dropout improves significantly when adding a real antenna! I should have been more clear about my son's situation. He does have a functioning attic mounted antenna (FV-HD30) that meets his needs. Here is a summary of earlier testing at his college apartment (within couple miles of current location).

I was asking for a traveling GH based on my hobby interests. For my purposes, it's easy enough to back the signal down with pad attenuators but I need available signal, thus testing at his place. You're correct, if I consider a traveling GH, it should be a gen 1 version. Your foldable GH looks intriguing!

Right now the I use the M4 as my positive control (UHF + VHF) and a radio shack indoor antenna as my negative control (VHF). I am pleased with the M4 but not many people in the general population are aware it. I first have to explain that it is a DIY antenna and then need to explain that no it is not the infamous utube antenna, it is much better!

I like the idea of a Winegard 7694 as a personal VHF gold standard since it is a readily available combo, has good data from Winegard, and would be a commonly recommended commercial antenna for many individuals with high vhf + uhf stations. The 7694 has higher vhf gain than the M4 and has published stats. Plus when I'm done, I could give it away to someone in my area.

For my next test, I'm building two high VHF antennas from Holl_ands pages (4 element yagi and 5 element yagi with folded dipole). To this group, a high vhf 5 element yagi by K6STI with folded dipole means something and could a positive VHF control when comparing/ranking antennas.

 

[300ohm]

Comparing high gain antennas in a super strong signal area like your sons can lead to some really weird results.

 

[IDRick]

Comparing high gain antennas in a super strong signal area like your sons can lead to some really weird results.

Please explain your comment... I don't understand why the results should be weird nor have I seen weird results when testing at my son's place. For example, the M4 was 2 to 4 dB higher than the M2 varying by channel and certainly within the range of testing sensitivity that I use.... What is the physics behind your comment?

 

[majortom]

with strong signals u can have multipath degradation, which where it's occuring has already degraded the signal by some amount.
hypothetically, let's say ur tuner's reporting a c/n of 21 dB on a really strong signal. agree, it should be reporting better, if the signal was truly clean and strong, right? now toss in a 6dB pad and u see the same 21 dB c/n being reported by ur tuner. what did u learn?

it's still a valid test, don't get me wrong, as some antennas may deal with it better than others for various reasons.
ya might wanna consider testing both ways though if possible, in a strong signal environment, and a
weak signal environment. That way u'd get some practical test results from both extremes...
and of course be sure to share your experience with everyone here too, hehe..

 

[IDRick]

Good explanation! Thanks majortom! I can use two methods for comparing antennas: measure output with an analog SLM or I can estimate based on the strong correlation between Signal Strength and margin to dropout on my Apex converter box. Adding attenuators is needed since it is not linear when signal strength is over 80%. I add attenuators to drop below 80% and estimate by equation. Estimates are within a dB of actual, close enough for a hobby measurement! Great point about testing in a high signal and lower signal strength area. I'll see what I can come up with.

 

[majortom]

Curious, what is the analog SLM?
have in-laws near nampa, anywhere near u? probly not.
never been.

 

[IDRick]

The Signal Level Meter is an analog device and the brand + model number are: Sadelco 719c. I live in Idaho Falls (eastern part of state) and my son lives in Boise (western side of state). Nampa is about 20 miles west of Boise.

 

[majortom]

Are all them oddball "-LP" stations really on the air, in analog and digital out there?

 

[IDRick]

Are all them oddball "-LP" stations really on the air, in analog and digital out there?

I haven't looked for the analog channels but would guess they are available. Most of the LP-DT channels were not available, regardless of which antenna I used. My son's apartment was on the 4th floor, clear LOS to towers on a mountain 15 miles away. Antennas were indoors, requiring the signals to penetrate one wall.

 

[300ohm]

When you go up there to compare, include in the tests a simple uhf loop, like the one that used to come with TV sets. If you dont already have one, they are all over the place at flea markets for next to nothing (or sometimes for nothing).


A loop behind a picture frame may be all he needs. If he has a large frame, my choice would be the Shorted Bowtie Loop.
Holl_ands has loop designs here :

http://imageevent.com/holl_ands/loops;jsessionid=3h9teyed51.penguin_s

My son's apartment was on the 4th floor

That implies concrete walls, which have metal mesh embedded, which will knock down the signal.

 

[IDRick]

My son is pleased with his current configuration and is not interested in making changes. I play with antennas up on his roof now and again just for kicks and giggles...

 

[IDRick]

What is the recommended feed separation for the Gen 1 GH? One diagram shows it at 44 mm while on another diagram by 300ohm, it appears to be >3 inches.

 

[300ohm]

After the original plans of the SBGH with the 44 mm feedgap was posted, more analysis soon after showed it benefited from a wider feedgap.

I used a 89 mm feedgap because that was the distance across the pvc tees I had, which provided a convenient stop block point for the wire, so it would hold in place nicely. In addition to the approximate .5 dBi average increase in Net Gain for free.

As you can see, the antenna will still work with a wide variety of feedgaps, but IIRC, after about a 115 mm feedgap, the elements would start to decouple. I would use an upper limit of about 105 mm to be on the safe side.