Sorry to pick nits, autofils, but you're talking about adjacent
is interference from another signal on the same
channel -- for example, channel 22 Burlington is co-channel to CBOFT-DT Ottawa.
As an advanced topic, one can talk about n-adjacent channels, for example, 23 is first adjacent to 22, 24 is second-adjacent to 22, etc.
This terminology also applies to North American FM broadcast channels, which are allocated 200 kHz apart on odd 100kHz centres. For example, your goal of 89.5 (Potsdam) is second-adjacent to local stations on 89.1 and 89.9, for example.
/end RF lesson
Sigh -- never mind, mlord got in while I was typing....
Looks like the "nit picker" race was on
Thanks for correcting my wording, I wouldn't want to mislead anyone.
Indeed, it is adjacent channel interference....what was I thinking ...!
Re 89.5 FM (potsdam): Thanks for the RF lesson.
I've modeled a GH4_VHF-Hi/FM combo that looks like it's worth a try. Total height is 53 inches.
20dBi Extended GH NarrowBand - Possible ??
I ran the extended GH8(jed) model by John Davis, and it shows peak gain at 614mHz with the following parameter values:
RawGain: 18.64 dBi
(Net gain is calculated at 18.56dBi)
We know from past modeling history for the SBGH, that the gain delta between a GH4 and GH10 is in the range of 2 to 2.5db. If you view this extended GH8(jed) model as "two GH4 type bays", it might have similar delta gain increases for more reflector pairs.
If so, a 20+dBi extended GH with total height of about 89" might be possible.
Who will put the "R" into R&D ?
Since this is an R&D thread, I will pose two questions for anyone interested in doing further research on the extended GH(jed) Narrow-band design ?
1. Can the gain be increased by 2dB or more by adding more reflector pairs?
2. Can the SWR over a channel's six Mhz bandwidth be further reduced?
From a construction point of view, each array element would have to be made with two sections, joined at the feed-point. Other than that, it should not be that difficult to build....just a few more right-angled array bends, but I'll leave that up to the "build-king" [mlord].