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Old 30-Jun-2013, 7:37 PM   #41
tripelo
Senior Member
 
Join Date: Jan 2010
Location: Dallas, TX
Posts: 123
Pete, your work with the antennas and especially the 8-bay is quite interesting.

The images of your setup are very good in that they show a descriptive block diagram of the setup.

There is some loss of S/N before any amplification occurs. Realizing that the reason for most of the loss is the filters and traps necessary to remove both strong FM signals and Channel 26.

Earlier, you mentioned:

Quote:
The PCT MA2-M’s don’t seem to overload, even without the notch filter.
Probably, the noise figure of the PCT MA2-M is better than either of the WG preamps.

Some S/N might be gained if, for UHF, the PCT MA2-M could be used instead of the AP-2870. Also, if the NF-471 could be placed after the preamp instead of in front of the preamp, it could recover the signal lost in the NF-471. To use the PCT MA2-M would probably require a UVSJ. Maybe something like this:

Code:
YA-1713 > FM Trap > AP-2870  > 
                               \
		               UVSJ > HDB8X Combiner > Power Inserter > ...
HDB8X > PCT MA2-M > NF-471 >  /
                                           /
                      CM-4228 > HDP-269 > /
Most UVSJ (Pico & Holland & some others) will pass DC through the VHF side.
The PCT MA2-M can be powered externally.


In your current configuration (last image in previous post), the gain on the CM-4228 side is less than the VHF/UHF combined side. Maybe this gain imbalance is necessary to have usable signals from the VHF/UHF side, if so then the PCT MA2-M suggestion above may not help because of the lower UHF gain of the PCT MA2-M (relative to the AP-2870).

Note: Previously, you mentioned concern about drop amplifiers being bi-directional. Normally, the forward bandwidth covers the CATV range 54-1,000 MHz. Whereas the return bandwidth is lower than ordinary TV signals, in the range of 5-42 MHz.

------------------

About your earlier comments regarding VHF reception of YA-1713 compared to CM-4228:

The YA-1713 accepts signals from a surrounding region of space (aperture). From the image in your last photo, both the 2-meter ham antenna and the CM-4228 may be interfering with the YA-1713.

Any metal inside an antenna's aperture can affect gain and pattern. The situation is usually worse when the metal dimension represents something approaching a half-wavelength at the frequency of interest.

Realizing that some people use CM-4228 in close proximity with a VHF antenna. Depending on relative positioning, such an antenna arrangement can, and likely does, affect an upper VHF antenna's gain.

The dimensions of a 4228 reflector are in the neighborhood of resonance at VHF, that is primarily how the 4228 provides gain at VHF.

It is conceivable that the YA-1713 could be aiding VHF reception for the 4228, and that the 4228 could be disrupting the pattern of the YA-1713.

Driven elements for 2-meter band ham radio antennas are not far in resonance from VHF-TV (~144 MHz vs 174 MHz). Directors for such antennas are shorter than resonance, so could potentially be a good reflectors for upper VHF.

Last edited by tripelo; 30-Jun-2013 at 11:42 PM. Reason: Note about bi-directionality of drop amplifiers.
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