[NLRS] 915 MHz ISM Band and Digital Modes

[Dr. Gerald N. Johnson]

I have some 850 MHz Micor that I think use a 30 or 50 MHz split. The 
first IF frequency is the split, so they use the TX oscillator for both 
TX and RX. They require modifying ceramic circuit boards to get them up 
to 902. I have considered using one for a 902 CW and very narrow FM 
transmitter some day. By very narrow I mean first order modulation 
products only as used on 2m in north Texas around 1965 and on HF 
earlier. Has the same amplitude spectrum as AM, just the relative phase 
of the carrier and sidebands is different so the AM receiver doesn't 
copy it, but a SSB receiver works very well exaulted carrier and it 
doesn't require a linear transmitter, class C works fine. Today I'd 
receive with my IC R7100 on 902 and 1296, maybe double from a modified 
FT-857 or the modified Micor or a 450 MHz Maxar I used to use on 9600 
baud packet with the audio turned down for the very narrow FM. I'd use 
another Maxar or a FT-857 with the varactor tripler I used for decades 
on 1296 but only on CW. With 10 watts drive from the FT-726 (that won't 
power on anymore) I got 2.35 watts at 1296.1 Good for eastern Ohio and 
Dallas Texas on the best openings.

I'd think the mid band 17 and 21 Mhz split repeater transmitters would 
encounter lots of QRM if the inputs weren't at the lower band edge. And 
the unlicensed users of the band would be annoyed by repeater TX output 
when the inputs were at 902. I have thought of hooking a multiband 
antenna to my R7100 to see how the noise is here in the country, but 
haven't.

73, Jerry, K0CQ

On 7/12/2016 10:09 PM, Doug Reed wrote:
>
>
> A previous revision to the Minnesota Repeater Council 902MHz band
> plan was about 10 years ago  when I suggested allowing repeater
> offsets of 17MHz, 21MHz, and 25MHz by keeping the output frequencies
> the same but allow multiple input splits. In the history of FM on
> 902MHz, some of the oldest rigs used 17MHz split, then Icom(?) had a
> generation that used 21MHz split, and now we all use 25MHz split
> because that is what the commercial rigs use on 800MHz and 930MHz. The
> Duluth repeaters are 25MHz split because they were built to use some
> GE radios that were common surplus about 10 years ago. The K0LAV
> repeater is the old 17MHz split and he will be updating it to 25MHz
> split when he gets the 930MHz transmitter running right.
>
>> From what little reading I did, it sounds like it is common in
> California to have 902MHz repeaters on different frequencies they
> reuse with different PL tones. Many of the repeaters have multiple
> receivers, or sometimes scanning receivers, to listen for adjacent
> signals which they then repeat. Kind of a poor man's trunking
> system.....
>
> 73, Doug Reed, N0NAS.
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