[NLRS] DEMI 2M Transverter using 26 MHz?

[Louis Sica]

Ah... didn't think about the need for two different antenna polarizations
for weak signal and local FM work... very good point...

-----Original Message-----
From: nlrs-bounces at mailman.qth.net [mailto:nlrs-bounces at mailman.qth.net] On
Behalf Of Jim Klassen
Sent: Monday, October 15, 2012 18:40
To: geraldj at weather.net
Cc: nlrs at mailman.qth.net
Subject: Re: [NLRS] DEMI 2M Transverter using 26 MHz?



I'd agree that in my experience, the feature set and easily accessible
controls I want out of a weak signal CW/SSB rig are very different than what
I want out of a FM/repeater use rig.  I used to be worried about finding
/the/ rig to do it all, but I find I am much happier keeping those two tasks
separate. 

Also, keep in mind you'll need different antenna polarization anyway.

73, Jim KB0UAZ

On Oct 15, 2012, at 12:11, "Dr. Gerald N. Johnson" <geraldj at weather.net>
wrote:

> 
> 
> I can't tell from the DEMI assembly manual whether the 26 MHz IF section 
> will have lower gain. There's an odd circuit that I don't understand 
> instantly but mostly the IF circuit has low pass filtration, the manual 
> says rolls off above 32 MHz. There's nothing in the RF section that 
> would degrade weak signal performance, just maybe that odd filter in the 
> IF. Even then some loss after the mixer should not affect 144.2 MHz 
> performance unless its so bad the IF receiver sets the system NF. With 
> 17 dB rated conversion gain, the RF stage pretty much sets the system 
> NF. Get down to 10 dB conversion gain and then the system NF will begin 
> to suffer.
> 
> I can't tell if the two 144 MHz filters have narrow bandwidth either. 
> Sent N2CEI an email but don't expect an answer for a couple weeks.
> 
> I built my first (and only) 2m converter with 26 MHz IF back about 1962. 
> It still works.
> 
> As for working 2m FM, the modern HF rigs probably won't allow FM below 
> 28 and there is FM down to 144.390 (APRS) and repeaters in the 145 to 
> 145.5 MHz region. Will your IF do 600 kHz FM splits? Does it have 
> provisions for subaudible tone? If not, you won't' be able to use all 
> the repeaters on the band. When a Chinese handheld costs not much more 
> than the special crystal for the transverter, and a decent kenwood or 
> yaesu new 2m mobile costs under $130 new and has all the offsets and 
> tones needed its not hard to think separate rig for FM.
> 
> I use a FT857 for HF, VHF, and UHF. It may be that I'd hear better with 
> a transverter, I've not tested that option. I hear well, I think and I 
> get out right now limited by my antenna not the rig. The 859 is not much 
> bigger than the DEMI transverter and has more options useful from 100 
> KHz to 470 MHz or wider. Its really handy to be able to tune NWS with it 
> that the transverter wouldn't allow up at 162 MHz and the FM mobile will 
> allow that.
> 
> 73, Jerry, K0CQ
> 
> On 10/15/2012 10:13 AM, Louis Sica, Jr. wrote:
>> 
>> 
>> Hello Group
>> 
>> Contemplating (again) my possible future journeys above 54 MHz...
>> 
>> Anyone ever use the DEMI 2M transverter using 26 MHz instead of the usual
28 MHz? I was wondering if performance degrades on the weak signal end of
the band when you do that, and if doing that even gives good performance on
the FM end of the band. Or should I just consider a seperate FM rig for
local chats?
>> 
>> ______________________________________________________________
>> 
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