Is it possible to use that same fixture, and see how the return loss might vary with frequency, and/or between pairs of baluns? Terminate one end to 75ohms, and sweep for return loss from the other end.
Could even take a step further, to see how the return loss of a stock C5 varies vs a modified C5, modified with some off the shelf balun in place of the stock balun. See if anything stands out? Not that there wouldn't be some variation between antennas also...

That's a good idea, but I have two complications on my end. Due to lack of a suitable indoor space, I have to put any test antenna outside in the parking lot and run cables back inside to the equipment cart. Maybe after the spring thaw... Also, the equipment that I have access to is all 50 ohm stuff. When using it with min-loss pads, return loss measurements are severely distorted due to reflections as to be only somewhat usable. I can see the general outline of the RL curve but cannot make precise RL measurements of 75 ohm antennas. Our design engineer has the state of the art equipment at his lab and can filter out these impedance distortions, but it is unlikely that capability will be added in-house due to expense and the lack of any real business need.

Wish I could do it...

Does anyone know anything about a channel master model no. 0035b outdoor balun?

Kind of an odd looking balun with bolts for the 300 ohm connection.

http://www.weisd.com/store2/CM%200035B.html

Eldgreen (re post #21).

You're right, as 300ohm alluded, the purpose of the boom is to hold the elements in a specific position. Check out the 100 element rope yagi, or the 'telerana' log periodic. These alternate methods of construction should work in an attic installation.

http://www.bigskyspaces.com/w7gj/longyagi.htm

http://www.ve7ca.net/AntLPD.htm

0035b outdoor balun?
It looks like it's designed to attach to a particular model of antenna. Don't know which one.

I just started building my own low cost antennas to receive some channels my dish doesn't carry. I see most of the 300-75 ohm baluns being used are the pigtail kind. In my junk drawer I found a push on type with F plug and screw terminals. Would this be fine to use along with a female-female coax joiner? Thanks.

It should work fine - is there a name/model number on it?

Kind of an odd looking balun with bolts for the 300 ohm connection.

http://www.weisd.com/store2/CM%200035B.html

The Channel Master 0035 balun internally is identical to the channel Master 0089. I have dis-assembled an 0089 and the core / windings are the same. The only difference aside from the packaging of course is that the 0089 is completely potted with a polymer type thermoset (urethane possibly). I believe the potting is what costs the 0089 in performance versus the Winegard TV-2900 which I have found to be the best perfoming overall wideband commercial balun. The Winegard has a smaller core and windings but is not potted. To verify my suspicions, I will test the 0035 and see if the larger unpotted core/windings match or exceed the perfomance of my TV-2900.

My lab tests of the CM 94444 (replaced the 0089) vs the TV2900 showed an advantage to the 94444 on UHF. Both were very good on VHF.

Balun pairs, back-to back. Sample size of one pair each.

http://i1203.photobucket.com/albums/bb390/AntDirect/wg_final.gif

http://i1203.photobucket.com/albums/bb390/AntDirect/cm_final.gif

Interesting. I can only test by tv tuner reception results. My reception seems to be slightly better with the TV-2900. Quality obviously varies with these baluns. I will dig out some more 0089 baluns and test them along with the 0035 I have. I have several TV-2900 baluns and they all seem to perform similarly.

Keep in mind I only tested a single pair of each model. The sample size is too small to extrapolate to the larger population of devices. Anyone who attempts to do so will be forced to watch Oprah for 24 hours non-stop.

I did a comparison of 10 pairs of the balun PCB used in our C5 antenna. Because this balun is hand assembled and was intended (optimized) primarily for high-VHF applications, there is a range of variability as shown below on UHf.

http://i1203.photobucket.com/albums/bb390/AntDirect/up2A-6batch1.gif

It should work fine - is there a name/model number on it?
It says SMK on the back below 75-300 ohm. Btw, do simple cable connectors like the female-female introduce much signal loss?

do simple cable connectors like the female-female introduce much signal loss?

If done properly, a very small amount, perhaps several tenths of a dB or less. If done wrong, they can loose all your signal.

I did a comparison of 10 pairs of the balun PCB used in our C5 antenna.Are these UP2A baluns available? I'd like to test these.

UP2A-6 balun is our designation for the PCB inside the "box" of the C5. It is not sold as a stand alone product as it's dimensions and form-factor are specific to our products. Unless you have a C5, it won't be of much use.

I also tested balun pairs labeled as from Magnavox and Eagle, all purchased from summitsource. Here are their response plots:

http://i1203.photobucket.com/albums/bb390/AntDirect/ea_final.gif

http://i1203.photobucket.com/albums/bb390/AntDirect/mag_final.gif


And finally, here's what our UHF PCBs (as used on DB2, 4, 8, & C4) look like. Note that this is 1 dB/div rather than the 2 dB/div on the previous plots. Very efficient on UHF, but brutal for VHF.

http://i1203.photobucket.com/albums/bb390/AntDirect/UP2ABaluns.gif

Just to make sure, in ALL of the charts, is 0 dB reference the MIDDLE line (fourth line up from bottom)???

Just to make sure, in ALL of the charts, is 0 dB reference the MIDDLE line (fourth line up from bottom)???

Yes, that is correct as denoted by the "MID 0 dB" annotation off the HP8569B's screen.

The "CTR" frequency is the center vertical line of the plot.

wow.. according to your measurements the TV-2900 actually dips at the start of vhf hi range and really falls off upper uhf. I'm defianately going to have re-compare with the CM balun.

Just wondering... anyone have plans on making a 300 to 75 ohm balun using toroidal cores? Without divulging much, I have access to a couple.