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1) Anyone have experience with the Digiair Pro ATSC spectrum analyzer (or something similar?). The RCA portable TV works reasonably well, but is slow to re-scan and does not give real-time information. Pricey, but I might have crossed the obsession threshold enough to purchase.
2) I understand combining two antennas for UHF results in at least 3dB signal loss, I think that is roughly half the strength? I don't really have a good sense for how that would affect reception (does the listing of NM(dB) or Pwr(dBm) in my TVFR help predict?).
3) The XG-91 has a mast-clamp system that allows tilt up, but I'm hoping I can find an optimal site for the BD4e (or something multidirectional, maybe even DB8e). Is there any readily available clamp solution that will allow me to tilt the DB4e or DB8e up 10 or 15 degrees? (mounting the mast at an angle seems difficult and less safe).
4) It seems odd to me that stations broadcasting from very similar/identical locations with similar power could have such variability in reception... is this due to frequency differences that cause different amounts of reflection and or refraction of the signals? For example, virtual 4,5,7,16 (real 38,48,39,31) all transmit from very similar locations, with kW ranging from 500-1000... yet are all very difficult to receive from the same antenna location. Any advice?
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#1: No, I have no experience with the Digiar product. I have been quite happy with the real time signal metering functions of the SiliconDust HDHR tuners. With a WiFi connected laptop or tablet, I can manually select any channel and observe signal strength and quality in real time while at the antenna, as I adjust location and aim.
http://forum.tvfool.com/showthread.php?t=820 &
http://forum.tvfool.com/showthread.php?t=14059
#2: Combining two UHF antennas gets very complicated, very quickly. If the signals from each antenna arrive at the combiner so that they are in phase (the positive and negative peaks of the signals occur at the same exact instant), you can expect more power at the combiner output. But if the two signals arrive at the combiner out of phase, and equal in amplitude, they can theoretically cancel each other completely. In practice, apparent loss can exceed 20 dB. The spec sheet for the Antennas Direct DB8E may help you visualize what can happen when combining two identical antennas, aimed at the same point and when aimed in separate directions.
https://www.antennasdirect.com/cmss_...s/DB8E-TDS.pdf Take a look at the various polar plots that depict the pattern and gain of the antenna as the panels are adjusted to various angles... Essentially, this is two DB4E antennas and a good broadband splitter/combiner with matched length coax cables from each section to the inputs of the combiner.
#3: None that come to mind... But scour through the hardware / mast / mounting options at 3starinc.com
#4: I can understand it seeming odd, but yes, the differences in frequency, exact antenna locations, power levels and the obstructions between the transmitting and receiving antennas all play significant roles in the differences you are observing. The wave lengths are all less than 3 meters... and the UHF frequencies are all less than 1 meter. As a result moving the antenna just a few inches can produce very noticeable changes in reception.