Here is the MINI Circuit TCM4-19..... and they do mean MINI!

http://img35.imageshack.us/img35/1569/newtransformer.jpg

It will be delicate to solder onto the surface mount pads. I have some copper clad board. I will try and twiddle on that, make a board to mount this and run wires from, or I will try and just wire direct... I just need some small gauge small (very) solid hookup wire to do it.

Is small the secret to low stray capacitance loss? May be bigger is not better for UHF right? The specs are excellent, with 0.99 dB at 100 Mhz and 1.23 dB insertion loss at 700 Mhz, almost linear. Now there are LOWER loss RF transformers at say 100 Mhz but they drop off sooner and faster at higher Freqs, say 400 Mhz. In the old days most stations, 90% of them, in the USA, all the big networks were on VHF 2-13, which peaks at 215 Mhz. However now in the USA for HDTV the emphasis is on 450 Mhz to 700 Mhz. There are few Hi VHF TV stations (one out of 18 in my area) and even less Low VHF, I recall about 40 total in all of the USA.....

This is a 4:1 Current-Type (Guanella) Balun..... it will be interesting to see how it works. I want to use a length of twin lead to mount it some what away from the antenna (say 7" to 28"), or I may try and install it, in the plastic "push-on" balun housing, I took the ferrite out of.

http://img405.imageshack.us/img405/3618/antennafeed.jpg

During my experiments I had jury rigged in the different baluns in. I have it so the balun is bolted to short copper lines right to the antenna (phase lines). It worked well. However it is to hard to bolt each balun, so to change them quickly I used some test leads. At first straight then twisting them.... Finally I took the twin lead off one of my TV rabbit ears. It was an improvement from the wires! This really did not affect my tests since I was comparing baluns and used the same basic test set up. May be instead of using the whole + 3 feet of twin lead a short section, 1/4, 1/2, full wave length of win lead would aid in matching and less loss?

Is it better than bolted direct? (don't think so but we shall see)

Is some hunk of Twin Lead to Coaxial a way to convert impedance, use some
clamp on ferrite's or low loss 1:1 balun for common mode noise suppression?


Also during during my experiments I was surprised that the dipole (rabbit ears) with of twin lead direct to coaxial to TV did almost as good as the BALUN. Got me thinking is that important, having 300 ohm twin lead feed line act to impedance match? Do the manufacture of the rabbit ear antennas pick that length of twin lead for a RF reason or just convenience to connect it to the TV? Coaxial can be used to match impedance, just not sure that helps match impedance by just connecting twin lead direct to coaxial. Of course there is the issue of balanced and unbalanced currents. I am going to look at signal strengths with and with out feed line before balun.

Well bought a drop amp, a PCT MA2-1P (same as a PCT MA2-M I think). It is 15 dB with a 2.7 dB noise number. I took the little Terk amp off (that came with the indoor Terk HDTVi antenna). With about 40' of coaxial and one 2-way splitter I got an average of about 4% to 5% more signal and a 2 to 3 dB more SNR. I suspect the old amp was good for a % or two signal? So this was a big gain.**

I bought this one used on ebay, to the door for $16 used. (they are $26 new + shipping) The other ones of the same design and rating (15dB) like the Motorola 484095-001-00, Winegard HDA-100, Channel Master CM3410 distribution amplifiers, all 15 dB amps, look alike. The 15dB amps are about $29 or more new + shipping. Motorola lists for more, not sure if it is better.


Right now I have about 3 feet of twin lead from the antenna to a push on balun, right onto the amp.... (From my previous experiments/) This may not be ideal from what I see. I had the balun right on the antenna before with coaxial from there, no twin lead, which I think was better. I just have not had time to go back to the original configuration. When I do I want to get before and after with this new amp.

**The drop amp was a big gain, but.... Of course all of you know that AMPS don't help if you don't have a signal to start with, but my cheap RG59 coaxial (going to replace that soon with RG6) and splitter losses were made up. I don't want to mislead any one into thinking this is a miracle thing and can get signals that are not there. I was shocked the gain was this good actually. Some of my previous signal measurements were done with out a signal splitter. With the amp it made up the difference and a big more. If you are running any length of coaxial and any splitters these are problem solvers.

If you read all the reviews of these drop amps (any quality brand) you will see some reviews say it did nothing for them (most admitting they probably did have a signal to start with). DON'T BUY THE CHEAP AMPS IN WALMART or RADIO SHACK... Actually they are not cheap, they cost as much as these good ones and have very high noise numbers. I read several positive comments in reviews about the difference going to quality amp, from previous "cheap ones". The cheap ones have more noise and you will pay the same or more for them. Order a good one. Plan about $40 to the door.... unless you can snag a eBay deal.

I will be going to go from about 30' of RG59 to about 60' of RG6, when I re-route the coaxial to it's final position. I hope 15 dB is enough, I am sure it will be if I don't add more splitters. I would recommend the Winegard HDA-200 has 24 dB gain with adjustable gain. That would have been better amp to buy simply because it is adjustable. However don't get a bigger amp if you don't need it. TOO MUCH GAIN CAN MAKE IT WORSE. The HDA-200 new is only $39 + shipping. That would be a good choice for longer runs or multi splitters, plus it has a FM trap if that is an issue for your (strong local FM radio stations). All these amps I mention are really indoor amps or need to go in a weather proof box or out of direct weather. The mast head ones are made differently. These do use a wall ward and coaxial cable to feed power to the unit (seperate from the signal coaxial).

I bought two push on baluns from radio shack and Ace hardware. I looked at them in the store. They looked different than all the rest, so I tried them. They were a tad better than my base line (the one with the biggest ferrite). Between the two I just bought, one had a small small advantage on a few channels. One had wires not as tightly wound on the ferrite and one wrap was not side by side but was over the other windings. This one was lacking ever so slight (as pictured below, good one not pictured but you can see one had neat windings, the "good one"). The "good one" is in the attic on the antenna. I think the one from RS was the "good one" but cost about $1.50 more. Ace was $4.29, RS was $5.99. Again too close to call, so a tie. The same with the two previous identical binocular ferrite baluns, the one with neater wiring was a tad better; seems the wraps should not cross over as it loops around the ferrite. Again small difference, not really that significant, but shows some varition in the same desgin and assuming same materials.

http://img21.imageshack.us/img21/619/tvbalun2a.jpg
http://img89.imageshack.us/img89/3845/tvbalun3.jpg
http://img819.imageshack.us/img819/6153/tvbalun1.jpg


Edit: part numbers of the two baluns, radio shack 15-1253 and ace hardware 30771. It is hard to say what they put in those boxes from one month to the next. I opened them in the store and eye balled them I could see they were different so I bought, glad I did. I'm going to use the radio shack one. The lesson here is not all baluns are the same. I might go try one with the short twin leads with lugs and a female F-connector at the other end, just for grins. (see pic below) If this has the same kind of transformer it should perform as well, my be better, due to better connection of a female F connector to coaxial. With the push on baluns, I need to insert a female F connector fitting to join coaxial to it, or use a short 300 ohm twin lead with the balun "pushed on" directly to the amp. Not sure what loss there is with a push on fitting?

http://www.radioshack.com/product/index.jsp?productId=2103912

What are the bandpass characteristics of such a balun? If centred on 94.5 MHz, where is it down, say 6 dB?I just recently acquired a 500Mhz network analyzer, HP 4195a. I can make some measurements.

I just recently acquired a 500Mhz network analyzer, HP 4195a. I can make some measurements.
Yes! Wonderful! Thanks for the kind offer.
Ben

What I've got here is the PC board from a UHF antenna. I ripped it out of it's plastic shell. An F connector is soldered to this board (those are the 5 solder pads showing in the middle). Two small bolts (1/8" diam, 1" long) are bolted to the two holes and they run through the plastic case where they connect to the active antenna elements. This is a single-layer board.

Please let me know if this balun has been discussed here before. Otherwise, if anyone has any idea how it works, I'd like to know.

I've hand-drawn a sort-of schematic above it. I'm showing the serpentine traces as inductors, but I think they probably function more like a strip-line or some sort of transmission line rather than inductors. It sort-of looks like a Marchand Balun, but my understand is that they don't work very well below 600 mhz.

I'd like to incorporate this design into an antenna amplifier I'm building, unless it's junk and not worth the effort.

If that design is not worthy, then I'd like to know if anyone has any experience with these:

http://www.minicircuits.com/pdfs/FTB-1-1-75+.pdf
http://www.minicircuits.com/pdfs/TRS1-23-75+.pdf
http://www.minicircuits.com/pdfs/JTX-2-10T.pdf
http://www.minicircuits.com/pdfs/TC1-1-13MG2+.pdf

http://www.fileden.com/files/2008/7/19/2010382/uhf-2.jpg

Please let me know if this balun has been discussed here before. Otherwise, if anyone has any idea how it works, I'd like to know.



Ken Nist discusses, and provides photos of, the PC board baluns used for the Channel Master 4228HD, AntennasDirect DB-8 and ClearStream 2 antennas here:
http://www.hdtvprimer.com/ANTENNAS/TemporaryPage.html

A couple of others are shown here: http://www.digitalhome.ca/forum/showpost.php?p=875418&postcount=97, and here http://www.digitalhome.ca/forum/showpost.php?p=884295&postcount=132

Here is a Patent Description for a Stripline Balun, showing several different implementations:
http://www.freepatentsonline.com/6294965.pdf
Note that you can search this website for either "Stripline Balun" or a specific Patent Number.

The meandering circuit trace is a constant impedance transmission line (like a coax)....and some
simply form a ground plane....and some are capacitors....and some might be inductors....

Several circuit traces can be configured to form a 1:4 o 1:1 (et. al.), just like a Coax Balun.
Capacitance and Inductance can be used to "tweak" the frequency response & matching....

While I don't know about efficiency/loss of these striplines, an advantage is manufacturing consistency (as compared to winding short wires on a balun), esp. in the sense of maintaining the design standard without testing each 50-cent board sold.

Wouldn't most kinds of balanced-to-unbalanced baluns change the polar gain pattern of an antenna a bit, each differently depending on the precision of your unit AND the frequency?

Ben

With my antenna I had the store bought "push on" type bolted to the antenna. This was a pain to test different baluns, so I used 3' of twin lead, to the balun....

Question should you bolt the BALUN to the antenna or use Twin-Lead, to the Balun, then coaxial. The alternative is balun bolted to the antenna then coxial all the way. The conclusion it did not matter and all coxial is a cleaner approach.

The last step in my mad scientist experiments to see if this Twin-Lead hurt or helped. The results were so close and consistent it was a tie... however some channels with the twin lead came in a better, a few % more signal, a few that dropped a little. I figured out it was because I moved the antenna a little. Where the gains and losses were explained solely by the antenna aim.

However with that said the SHORT TWIN LEAD section from antenna to BalUn did not hurt! It was may be a tad better! With that said for practical reasons I don't recommend it. Coaxial is just easier to deal with.

I never tried the "outdoor" baluns, the ones in a tube with a short bit of twin lead with lug spade terminals. Those might be better? I will not know. The way the push on balun plugs onto my antenna I don't want to change that. I could, but I am tired of messing with it and now all my signals in 4 directions, each more than 30 degrees apart, over 210 degrees from 20, 30, 40 and 60 miles all come in great.

The only negative is on two strong stations, I see some instability, the signal gets a little jumpy. This is no doubt form the drop amp I added over driving may be? It's only on two stations and does not affect the picture. This is the problem with trying to get near and far stations in different directions from one fixed antenna. It really should not be done, but I DID IT! :rolleyes:

Regarding the PCB BALUN - Obviously there is no ferrite involved; it is using air as the core. The way that one is wired is a variation on a 4:1 Current-Type (Guanella) Balun it looks like.

http://homepage.mac.com/kenwetzel/Low_Loss_Balun_files/image001.jpg
ref http://homepage.mac.com/kenwetzel/Low_Loss_Balun.htm

What has always bothered me, is unless you are using a loop, folded dipole, like a Yagi with a active folded dipole element, which is 300 ohms, then a 4:1 balun is not correct. The open "Bow Tie" antennas are not 300 ohms, may be 150 ohms? Further their impedance varies with Freq, as all antennas do. However 300 ohms is handy because it is divided by 75 ohms, the approx impedance or RF in air. From playing with a 2:1 balun is it does not make much difference! There are going to be losses and mismatch. Your best bet is get the best antenna (directional is best) as high as you can to over come any loss you have in the feed line. As I said a amplifier is not magic and just overcomes some feed line loss but can cause other problems. If you don't need one don't use it. As well the ideal situation is one antenna per TV and no splitters.... once you split the signal you cause big loss in signal then you need an amp... Amps amplify not only the signal you want but all kinds of other signals, which can add to the noise and multi-path errors.

sumguy99

I got a Mini Circuit TCM4-19 and it did OK, very good on high VHF. It was just not quite up to the dedicated TV baluns. I also got two CoilCraft RF transformers, and again not quite up to the same signal as the dedicated Baluns. The TCM4-19 is nice for FM radio, but it only has about 1.24 dB loss at 700 Mhz. All the 4:1 baluns start to fall off above 500 Mhz. I'm sorry I did not see the MiniCircuit 1:1 baluns to try.

The first one in your list does not have the Freq range for UHF 450-700 Mhz, seems to have high insertion loss. The voltage baluns (complete isolation) not sure how well it would work. The current balluns, where there is no isolation may be good, but not sure how that will handle the balance and unbalance.

ONE THING YOU MUST KNOW... they are TINY! You know a postage stamp 1.8" x 1.3". These little guys are less than 2% the size of a postage stamp... They are very small, 0.15" x 0.16" - I was able to solder small wires onto it and put it into a push on TV balun housing. It worked well. Have to be careful soldering metal pins in plastic.

What has always bothered me, is unless you are using a loop, folded dipole, like a Yagi with a active folded dipole element, which is 300 ohms, then a 4:1 balun is not correct. The open "Bow Tie" antennas are not 300 ohms, may be 150 ohms? Further their impedance varies with Freq, as all antennas do. However 300 ohms is handy because it is divided by 75 ohms, the approx impedance or RF in air. From playing with a 2:1 balun is it does not make much difference! There are going to be losses and mismatch.
I've NEVER run across a Bowtie antenna with a 150-ohm Characteristic Impedance, with or w/o Reflector.
In addition to Ken Nist's DB-2a 4nec2 file, ALL of these are 300-ohms (+/- 50-ohms):
http://imageevent.com/holl_ands/dipoles
http://imageevent.com/holl_ands/multibay

Note that new Supersized Multi-Bay Antennas have much better Gain and SWR characteristics
across the New UHF Band than their older counterparts (e.g. CM4221, CM4228).

And why 4-Bay UTube Defect posted by babblin5 (using WAY-TOO-SHORT coat hangers and a 2x4)
should be discarded...

Of course the "Stick Dipole" has a Characteristic Impedance of 75-ohms (+/- 10-ohms) with a
very narrow range of low SWR....this greatly improves when Yagi passive elements are added,
but it's easier to get a good SWR when you start with a Folded Dipole:
http://imageevent.com/holl_ands/loops

holl_ands

Thanks... I scanned over it, great links! Take me awhile to digest it. I see where I got it wrong.

http://www.hdtvprimer.com/ANTENNAS/comparing.html
or specifically
http://www.hdtvprimer.com/ANTENNAS/TemporaryPage.html

My mistake. He was talking about the 4228 antenna (two 4-bays) needing a 2:1 balun.... He states it's two 300 ohm antennas making a 150 ohm antenna.... So you are right. I made a typical 4-bay, on PVC with 9.5" spacing and 10.5" elements (should be 10" just did not trim them and it works so well why change it). It's 300 ohms (nominal) +/-50 ohms, good to know.

I am still confused on TV Rabbit Ears...not folded dipole but dipole, about 75 ohms, but used twin lead 300 ohm wire. I am talking old time 300 ohm two terminal antenna inputs of analog TV's. Apparently the TV rabbit ear impedance varies with Freq, height above ground, angle between "ears". From the link about the UHF Stick Dipole is 75 ohms... so that makes sense. However why did they use 300 ohm twin lead? Compatibility? Being such a short length of feed line I guess it does not matter.

Bowtie antennas are fullwave dipoles, not halfwave dipoles, so their impedance is higher than 75 ohms.

holl_ands

I am still confused on TV Rabbit Ears...not folded dipole but dipole, about 75 ohms, but used twin lead 300 ohm wire. I am talking old time 300 ohm two terminal antenna inputs of analog TV's. Apparently the TV rabbit ear impedance varies with Freq, height above ground, angle between "ears". From the link about the UHF Stick Dipole is 75 ohms... so that makes sense. However why did they use 300 ohm twin lead? Compatibility? Being such a short length of feed line I guess it does not matter.
In old VHF Band Rabbit-Ears, they used 300-ohm twin-lead because that was what everybody used.
Old TV sets only had 300-ohm twin-lead connections and very few people used high loss RG-59 Coax.

I think that when I was a kid in the 50's, there was pretty much only Ch2-6. With wavelengths
under 12-feet, it would be quite difficult to set up much of a standing wave on a short cable....

So-called 75-ohm impedance can ONLY be met over a narrow range of frequencies:
http://imageevent.com/holl_ands/circularpolarized/rabbitears
Low SWR for 75-ohms is barely achievable over just the Hi-VHF Band (Ch7-13), but ONLY
if the whiskers are extended to the correct distance....and who wants to get up to adjust
the whisker length every time they change to/from a Lo-VHF station?????

I added Gain, SWR and Impedance sweeps for the full Ch2-13 VHF Band, presuming
connection to a 300-ohm load. In the Hi-VHF Band, the SWR is four times higher than 75-ohms,
and on lower channels it climbs to extraordinarily high levels as the Impedance becomes
nearly all Capacitance (negative Reactance). So, basically they ignored SWR...which could
be a problem for DTV.

RCA ANT110 Rabbit-Ears+Loop Antenna interior photos are also found in the folder.
It has a 75-ohm coax connector, and it appears that they used several different types
of spirals and zig-zags in the circuit board plus capacitors to "adjust" the Impedance.

Amplified Antennas can improve on this impedance matching technique, since
they are less constrained in how they improve the SWR.

==========================================================
This 1979 NTIA Report provides Gain & SWR curves for a number of TV Antennas available
at that time, including VHF Rabbit Ears with 12-position rotary "Tuning" switch:
http://www.its.bldrdoc.gov/pub/ntia-rpt/79-28/79-28.pdf

Here's Kerry Cozad (ex-Dielectric Antennas) VU-Graphs re UHF ONLY Antenna Measurements,
including R-S 15-1864 Rabbit-Ears+UHF Loop:
https://secure.connect.pbs.org/conferences/technology/2005/Presentations/DTV.Receive.Antennas.ppt

And finally, here is Marcoux's Report which reassessed the so-called DTV Planning Factors,
which includes some other Antenna Measurements (careful, some are for worst-case freq):
http://www.ccbe.ca/Downloads/CCBE2009-RevisitingDTVminFS.pdf
This On-Line Calculator facilitates conversion between SWR and (Marcoux's) Return Loss.
It should be familiar, it's same thing as "Refl Coeff (dB)" just below 4nec2's SWR Plot:
http://www.microwaves101.com/encyclopedia/calvswr.cfm

holl_ands

Thanks... I scanned over it, great links! Take me awhile to digest it. I see where I got it wrong.

http://www.hdtvprimer.com/ANTENNAS/comparing.html
or specifically
http://www.hdtvprimer.com/ANTENNAS/TemporaryPage.html

My mistake. He was talking about the 4228 antenna (two 4-bays) needing a 2:1 balun.... He states it's two 300 ohm antennas making a 150 ohm antenna.... So you are right. I made a typical 4-bay, on PVC with 9.5" spacing and 10.5" elements (should be 10" just did not trim them and it works so well why change it). It's 300 ohms (nominal) +/-50 ohms, good to know.

That's not what I got, using dimensions directly off my CM4228HD:
http://imageevent.com/holl_ands/multibay/8bayrefl/cm4228hd

I just checked for "best" SWR match: 265-ohms, New UHF Band SWR is under 2.08.
At 300-ohms, New UHF Band SWR is under 2.14...hardly any difference...

I'm building an attic-mount SBGH-6.

I don't want to go up in the attic more than necessary, so I'd like to solder the balun connections to the feed points.

I'm using #4 solid copper for the elements, which I've already tinned to ease soldering. I plan on cutting off the horseshoe shaped connectors on the balun leads so I can strip the wire, tin it, and wrap it around the #4 copper before final soldering.

Because of the spacing between the feed points, the balun leads will have a hard time reaching.

1) Can I split the bit of twin lead coming out of the balun to give me more spread in reaching the feed points?

2) If I spread in this manner, is it okay that the balun leads are at 90 degrees to the balun and the balun itself is now suspended right in the middle of the feed points and pretty much on the same plane as them? And does it matter how close the split gets to the balun?

3) Would I be better off adding lengths of wire to the balun leads so it's further away from the feed points?

4) If adding wire, just separate individual pieces? Or 4-6 inches of twin lead (which I would end up splitting at the end to reach the feed points)? And should the wire be insulated or not?


Thanks to anyone for any help you can offer.

Just hook it up already and quit obsessing over the small stuff....

Just hook it up already and quit obsessing over the small stuff....


If I had known it was small stuff, I wouldn't have asked. Will give it a whirl.