Winegard vs. Jack antenna (again)

Good thought. I didn't remember seeing you had one.
I also looked at the SensarPro and have the plot around here somewhere. But you're right, they are roughly 1db steps with '10' being aprox. unity (its +-10db). Its not dead accurate but certainly good enough to see if the Rx AGC is doing your test in. Dunno why '0' doesn't shut power off, I think mine does.

Its always possible you have a cap or transistor thats just fallen out of spec.I guess. UHF can be unforgiving far more than the low bands. Probably easier to shotgun the board, or see if you can get someone to donate one to the cause. There are several here that have sacrificed their Batwings to the great god of Oak

Jeff,
I don't have any pads so I hooked my Tech3 to the output of my SensarPro. The gain settings go from zero to 20. Zero being no output and one is 9db attenuation. 20 is 10db of gain approximately. With the batwing installed I tuned to the strongest station and varied the gain from 1 to 20. The output measured from 17db to 39db and tracked linearly, approximately 1db per step. I then tuned to the weakest station and results where levels from -5db to 19db. I did the same thing with the Jack. The levels where different but linear.

I did notice that the SensarPro continues to supply power when the gain is set to zero.

I did manage to open up my batwing without destroying it. There is zero weather proofing, but the amp and connections looked good. I removed the amp and cleaned the connections just to be sure. This made no improvement.

Tom_M wrote:
Jeff,
I didn't know that you had tested a second Jack. It appears that I have a problem with my batwing. You did an exceptional job with your test and I'm sure that the community appreciates your efforts.

Thanks.

I never mentioned it cuz he came by curious what I was up to (we have no life and hang at the storage lot. Think Hank Hill...). Anyway he asked if I could check his and I said "sure"... and kill 2 birds with one stone. He gets an antenna checked and I get a comparison.

I'd sure be curious whats causing that myself. We have 2 of those demods in Salt Lake. I'll see if I can get the local guy to run the input pad test on them.

Jeff,
I didn't know that you had tested a second Jack. It appears that I have a problem with my batwing. You did an exceptional job with your test and I'm sure that the community appreciates your efforts.

Thanks.

I know what they are. I have probably 30 of them scattered around the country to stream our various channels around the company, and we have several locations with stacked DS-3's to support these things. You can call it a 'Pro' receiver, but it certainly is not an off-air broadcast grade reference receiver. And I agree that it makes no sense to do post AGC, but it's done on receivers all the time. Go figure...

Jack Antenna: There was nothing wrong with the Jack. The neighbors RV next to me has one and he let me plug into it briefly. The two were essentially the same. I'm not here to argue my data or have someone question the equipment. You mentioned that the data doesn't track and you are correct. I'm simply pointing out you cannot use a receiver to do what you want to do, and it's pretty obvious from your post you're technical enough that you know that.

You essentially did the test with the same generation Batwing (2005 & 2006), and a new Jack. So something is obviously different on your UHF

Jeff,

The HDHomeRun Tech3 is not a consumer receiver. It's described as a commercial broadcast and cable diagnostic/troubleshooting device. The consumer version is the HDHomeRun DUAL. If the signal levels reported were skewed by AGC that would make the readings useless. It would make no sense to pull signal strength measurements after the AGC circuit.

Even if I had access to a spectrum analyzer, it would not tell me if my batwing was defective. The only way for me to tell will be to check another batwing. Likewise you don't know for sure that the Jack you tested was not defective.

Tom_M wrote:
I'm actually on the east side of Lake Okeechobee near Indiantown.

As I said in my post, I think that more testing is needed to come to a conclusive result. I have another Batwing antenna, but it is not amplified. I don't know the gain of the preamp in the amplified version, so testing that one would not prove anything.

IF you prove your amplified batwing IS good, the delta between the two will get you gain.

Also if you have a set of 75ohm pads laying around (like 10db), try those in and out of line post power supply. That should show you what influence, if any the Rx AGC is having. If it doesn't perfectly track, then you'll know its skewing your test.

Mark: Mine was done in Valencia in North LA County that has a clear shot to Mt. Wilson, and is shaded prettymuch on all sides by mtns. But that's also why I did the angular tests. It's a single point source for everything from channel 7, all the way to the top of the UHF band.

Tom: You cannot do 'real world' antenna gain tests with a consumer receiver and have definitive numbers. All you can do is see how the receiver reacts to different antennas, and the AGC is the main reason why. When I said that the numbers are off, they are off in relation to the two antennas which the AGC obviously influences, and not necessarily the same. It it possible for the Jack to not have enough gain to hit the AGC threshold, and also possible that the Winegard to have just enough gain to get into AGC threshold to force the receiver to roll back a little. You also don't know if your sample metering is pre or post the AGC circuit. See the problem? (Edit) And thirdly you may actually have a problem with the Batwing. But how do you know.. ? That's why I went to the trouble of bringing the big hardware home for the measurements. You can see by the setup on the screen what the setup is, and the analyzer cannot be fooled by internal automatics because it has a none. And because I have a calibrated receiver (the analyzer) that cannot be fooled when I did those, and known good antennas, I said if anyone says the Jack performs better, the Batwing is broken. The problem is that your comparisons look correct on VHF, but the UHF is definitely not what I'd expect to see. So...... ??

As for measuring the actual gain of each antenna, it's impossible unless you can shut off all of the receiver automatics. You also don't have a calibrated antenna reference that you can say this is my unity gain antenna and all other measurements are referenced to this zero (unity) gain source. And if you really want to do it right, then you measure the antennas against the reference without preamps. I wasn't interested in cutting antennas open, nor have any experience with calibrated antennas. Maybe our resident antenna design engineer can comment on that?

Actually I moved the marker SE of town. My typo. Not enough coffee.

Have you used TVfool to locate the transmitters and your actual distance from you? Clicking on each transmitter site gives full information on each for comparison to your numbers.

Mark

I'm actually on the east side of Lake Okeechobee near Indiantown.

As I said in my post, I think that more testing is needed to come to a conclusive result. I have another Batwing antenna, but it is not amplified. I don't know the gain of the preamp in the amplified version, so testing that one would not prove anything.