[aprssig] 9600 baud capable radios
ralphmilnes at patmedia.net
Wed Feb 2 14:24:41 CST 2005
I'm a bit confused by the 9600-capable radio thread:
Henk seems to be saying most radios billed as 9600-capable are NOT
>Any "staight" design with direct modulation in the PLL loop will fail,
> unfortunatly this accounts for 99% of the Ham radios from Japan..
George says the V7A and D700 are OK. Henk do you agree with that?
George says V7A and D700 do need a good signal path, and Gerhard points out
that the minimum TXDs on the V7A and D700 are relatively high and thus
reduce the overall effectiveness of quick 9600 exchanges.. so they are not
ideal for a 9600 baud network (for example at the node).
But I want to confirm whether or not the V7A and D700 (and the D7A?) will
still function at 9600 as advertised. The answer will be useful for users
who are trying to use these Kenwood radios for "simple" communication on a
Henk, do you have any examples of the #2-type radios you mention below?
(In digest mode)
This makes a normal PLL box unsuitable for 9600 baud, at least when using a
signal according to G3RUH. Now there are some ways to make a good 9600 baud
(or better) radio:
1) Use a radio with a crystal oscillator. So your old TR7200 from of arround
1980 might proof to be a very good 9600 radio. Remember we need a flat
envelope from 10 Hz to 8 kHz so we have to bypass the audio amplifier with
all its capacitors and modulate> the VXO almost directly. Also the special
TEKK data transmitters use this.
2) Use a PLL VCO and mix the output with an FM modulated VXO - so not
modulate in the PLL. The output of the mixer is then your signal. This is
the kind of radio I use. A telephone is full duplex and a modified Nokia car
telephone is very suitable. It uses one PLL VCO simutaneously for
transmission and reception, for transmission the signal is mixed whith an FM
modulated VXO. RX/TX changeover is very fast since the PLL VCO doesn't
change frequency. Some modern multiband radio's also have this, they are
excellent for 9600 baud.
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