RE: WOGX and the 4221A vs U-75R
This is the kind of story that makes me wish I had a 3000 mile long piece of coax.
Originally Posted by Piggie
It would have been enlightening to have had the opportunity to do a comparison of those two installations; to have been able to compare not only signal levels but also to have stared at the two waveforms on the spectrum analyzer for a while. The questions are how flat was the waveform for each antenna, and to what degree do any observable serrations vary over time?
I could not find any vertical or horizontal polar pattern specs for either antenna. I have to say this is one thing I appreciate about the Winegard Company. What ever they've got, they've got, and they're not afraid to publish real engineering data.
I went to Winegard to find comparables to see what their characteristic polar patterns were. Their HD4400 (a 4-Bay BowTie), as a comparable to the 4221A, shows a horizontal 3 dB beamwidth of 46 degrees at Ch 50 (close to WOGX's 51). Their HD9075 (a Yagi), as a comparable to the U-75R, shows a beamwidth of 32 degrees.
So this may have been a factor; maybe some reflections creeping in an out of the aperture. But the HD9075 also shows about 3dB higher gain than the HD4400. This could also have been a factor; maybe just enough additional margin to keep you above the cliff.
If we had some real data for the 4221 and U-75R maybe we could draw some conclusions. Sigh.
Wish I could've seen 'em...
I'll be having crow for dinner; medium well, thank you.
I'm really shocked at this, but after my last skeptical post about the CM4228's claimed 9 dB Hi-VHF gain, I had a "Boing. I should've had a V8!" moment.
I have both a CM4228HD and a Winegard HD7698P mounted 85' up in a Pine tree at the moment. The 4228 is about 4 degrees off the 7698's LOS, the later of which is optimally pointed for 7-13.
So I dragged the analyzer up to the porch to capture both signals, and here is the resulting comparison.
I have to say I'm chagrined. Moreover, I'm even more of a bing-bong because after sniffing around in a capture directory I found a similar set of captures done back on November 12, and they are quite similar.
Now, I've previously compared the Y10-7-13 to the HD7698P and the Y10-7-13 is just 1 or 2 dB hotter at the ends of the band (7 & 13); e.g., pretty close to the HD7698P.
So, while there's a dramatically poorer envelope from the CM4228HD (much more significant multipath impact, in conflict with my theories about N-Bays vs Yagis) the absolute levels are within a few dB of each other.
Two caveats. (1) The off-axis pointing of the CM4228HD may be having a slight effect on envelope flatness, but I would only expect a rather small change if re-pointed 4 degrees, not a dramatic one. (2) just to be up front, the amplifier in the CM42228 path has about 3 dB higher gain than the one in the 7698 path. But I corrected for that on the analyzer's level setting prior to capturing. I think any errors here are within a few dB.
The point is, there's not an order of magnitude of difference between the two. Rather, poorer wave shape aside, the levels are actually pretty close!
[Could you pass the salt & pepper please?]