From: Paul Keinanen
Subject: Re: transverter design for 20 meters?
X-Newsreader: Forte Agent 1.92/32.572
Date: Mon, 23 Sep 2002 09:36:45 +0300
NNTP-Posting-Date: Mon, 23 Sep 2002 09:35:07 EEST
Organization: Jippii Customer
On Mon, 23 Sep 2002 06:36:49 +0200, "JC"
>I think transverters are used for increasing the working frequency not
>decreasing it, i.e. passing from HF to VHF. I never saw plans for passing
>from 10m to 20m or even 80m.
At least in England, there has been kits for allowing 2 m multimodes
(such as FT-290) access to the HF bands using a transverter.
>The contrary would be easier as 10m is an
>harmonic of 20m or 80m.
This is just a situation you try to avoid.
For instance a transmitting converter from 28 Mhz to 144 MHz often
suffers from these harmonics. Assume you want to transmit on 145.100
MHz on a repeater input and you set the HF radio to 29.100 MHz. The
5th harmonic of that is 145.500 Mhz, which falls in the middle of the
FM calling channel :-).
Thus, you have to be very careful to filter out any 5th harmonic from
the HF signal and also take care that the mixer does not generate any
larger amounts of 5th harmonics of the input frequency.
In general you should design the frequencies in such a way that no
harmonics from the low frequency signal or the local oscillator signal
fall close to the desired output frequency band, since it would be
very hard to filter them out, once they have been created.