There are a few syth'd radios which can be modded to run very well.,
these are the ones which use an interpolation oscillator to mix the vco
to the required frequency. As the interpolation oscillator is outside of
the pll, it can be fm'd without problems. further more these radios are
usually fairly cheap, with filters like barn doors. Please dont ask for
type as I've forgotten !!!, but they were low end market japanese 70cms
rigs. these rigs are easy to spot if you can get hold of the circuit
diagrams, you know those funny diagrams with lots of squiggles on !!!
73 richard g8jvm
In message <[EMAIL PROTECTED]>, Bob Nielsen
<[EMAIL PROTECTED]> writes
>On Thu, Dec 09, 1999 at 08:55:48PM +0100, Thomas Sailer wrote:
>> Bob Nielsen wrote:
>> >
>> > On Wed, Dec 08, 1999 at 03:45:40PM +0000, Patrick Ouellette wrote:
>> >
>> > > Most of the newer mobile radios from the major manufacturers include
>> > > 9k6 ports.
>> >
>> > Have you found any of these to actually work (low BER, txd < 30 ms or
>> > so)?
>>
>> Good question. Henning DF9IC has measured a couple of mobile
>> transceivers
>> claimed '9k6 capable' about 3 years ago, and none was satisfactory.
>> I've heard of new allmode transceivers (one ICOM model) that works well
>> with 9k6, that is however >$2000.
>
>That was my point. I believe QST came to a similar conclusion. The
>allmode transceivers tend to use a heterodyne scheme for transmit so
>that you modulate a crystal oscillator stage rather than the PLL. As I
>recall, an early Azden FM transceiver did this as well and had
>reasonable 9600 performance.
>
>Otherwise there is a trade-off between poor frequency response (fast
>PLL time-constant) and poor T/R switching times (slow PLL
>time-constant). There are ways to compensate for the frequency
>response, but it's a bit tricky and may not be all that stable in a
>production-line radio.
>
>TEKK and some other data radios work fairly well, as do some converted
>crystal-controlled commercial radios, such as Motorola Mitrek.
>
>>
>> In the end you're probably better off with dedicated designs like
>> the T7F kit by Holger Eckhardt.
>
>Do you have a URL for this?
>
>Bob
>
--
richard bown
