[OZAPRS] 30m port

[Ray Wells]

Nick Mclean (SYD) wrote:

>Hi All,
>My experience with 6801's and all Codan products has been good, they are
>normally very robust. I am surprised you have had a failure running 35
>watts on a 100 watt PA.
>73's 
>
>
>Nic McLean
>
>VK2KXN / VK5ZAT
>
>Tel:  02 99410619
>
>Fax: 02 98139009 
>
>Mobile:  0417 822 728
>
>
>
>Tim,
>
>It's a Codan 6801. No dramas with the radio itself but I've had three
>Codan PA's suffer from failed PA transistors. Two in a Codan 7727 and
>one in the 6801. The radios are pegged back to about 35W so they're not
>being worked to death. They were on two different bands as well.
>
>I use an MFJ1270B TNC that hangs off xastir on the Linux BBS machine.
>
>Ray vk2tv
>
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>
Hi Nick,

It surprises me somewhat as well. Actually I got the failures wrong way 
around. It was once in the 7727 and I pinched the PA out of the spare 
7727 radio, and twice in the 6801 (the PA's are almost identical - same 
PCB, just a tx/rx switching difference). With the 6801, once was on 40m 
and I suspected that was due to the switch contact to the LPF going open 
- the rx was deaf until I moved the switch - and the PA transmitting 
into an open circuit.. When I put the 6801 on 20m I hard wired the LPF 
to bypass the switch to avoid that possibility but had another failure.

I've considered RF from the other HF transmitters getting into the PA 
but given the isolation between antennas, the level would be 
insignificant. The 20m and 40m dipoles are vitually end to end, and the 
30m dipole is some distance away, and at right angles. The first failure 
was in the 7727 and that was before the 20m dipole had been erected.

The Tracker Lynx (was on 30m, now on 40m) uses an almost identical PA 
arrangement and it's just plodded along for years.

Given the robust nature of the Codan PA design, and the lack of any 
definitive reason for the failures, I'm inclined to suggest I've just 
been very unlucky.

Ray vk2tv
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