I have never trusted that method. In theory it works fine. But...if the ALC
fails, or the TIB or other source of negative voltage fails, or the radio puts
out a high power spike as Eric mentions (and many do), it's back to the shop.
In my case, I dug into my IF rig, a TS-690S, and brought out the driver signal.
A relay switches it between the transverter and the rig's finals. It's a
simple mod, if you can find room on the rear panel for a couple of connectors.
I used SMAs, which don't take up much space. I got the idea from an article
written by Rus Healy, K2UA, in the January 2000 QST. Although I implemented it
a bit differently, the article is worth reading.
Good luck!
Bruce WW1M
>
>I think you just nailed the reason many people use the 817 to drive
>their DEMI gear. Since the TX won't make more than 5W even in it's
>highest power mode, you don't have to worry about cooking your shiny xverter.
>
>Because I don't want to incur time for repair on the units, the last
>thing I want to do is cook them with 100w spikes on TX due to ALC,
>even if only for a few seconds. Running the bands with several
>multi-op stations at each new grid can really add up.
>
>I know the 857 has a low power jumper on the power input cable. If
>you ground it, the rig is supposed to put out no more than 10W. Not
>sure if this is via ALC or if it somehow bypasses a PA. In any case,
>if you only had a 857 that route might be worth investigating. Not
>sure if the 847 has this feature, check it out.
>
>At some point I'm going to switch over to the low power flex radio
>SDR, which is also a nice IF rig power wise.
>
>I'm curious to see what the results of your o-scope work finds. Please post!
>
>Have fun on 900!
>
>kr0ver
>
>At 09:30 PM 2/2/2010, you wrote:
>>I used it in the January VHF SS with the
>>power control set to minimum on 144 MHz to drive my 903 DEM transverter
>>with no problems.
>
>_______________________________________________
>VHFcontesting mailing list
>VHFcontesting@contesting.com
>http://lists.contesting.com/mailman/listinfo/vhfcontesting
_______________________________________________
VHFcontesting mailing list
VHFcontesting@contesting.com
http://lists.contesting.com/mailman/listinfo/vhfcontesting
|