[TenTec] re Orion II curiosity

[joel hallas]

Rob,

Well put on all points!

One other thought would be that a test into a good, solidly connected, 
dummy load should eliminate RF as an issue and verify proper operation 
under even more ideal conditions.

73, Joel, W1ZR

Rob Atkinson, K5UJ wrote:

> There can be more than one cause of low p.o. if in fact it is really low.
>
> as others have mentioned the first thing you need to do is have a way 
> to measure peak power.  you need to get either a true peak reading 
> meter (uses some kind of dc source, usually a battery or a wall 
> adapter) or use an oscilloscope with the trace slowed down enough to 
> catch the peaks.  Since a good peak wattmeter is about as much as a 
> good used oscilloscope you may as well get a scope if you don't have 
> either since you can do more with it.  you can get a good deal on a 
> tek 465 from http://www.testequipmentdepot.com
> one possibility is that your orion is just folding back from a high 
> vswr into either an antenna or amp.
>
> another cause of low power out is agressive AGC response.   It's a 
> little known fact that some rigs (all mfrs. not just ten tec) are 
> sensitive to rf coming back to the rig; this affects the agc circuits 
> in some way to provoke a response that causes the rig to do a false 
> positive and limit p.o. below its spec'ed peak.   I say little known 
> because, if a ham has a rig at a location where there is plenty of 
> room for antennas as opposed to a ham on a small lot with the 
> feedpoint right overhead, he may not notice anything amiss.
>
> I'm not an engineer and don't pretend to be one; all I can say is that 
> I have had big AGC responses with rigs, limiting power out and there 
> was nothing wrong with the way the rig was adjusted or aligned, I 
> simply had to take a number of measures to limit returned common mode 
> rf (line isolators, ferrite chokes on mic and key lines, even removing 
> the ground strap in some cases) but after doing that, the AGC response 
> calmed down and the rig behaved as advertized.
>
> I have a theory that manufacturers measure performance and test out 
> rigs in nice ideal condtions--maybe the rig is on a bench with an 
> antenna on a tower a few hundred feet away--
> and everything seems to operate okay on air so they don't bother with 
> a few ferrite beads and shunt caps in choice spots inside, then joe 
> ham gets the rig and, with a dipole hanging right outside overhead, 
> has these mysterious problems.
>
> it's a little bit harder to measure or view your AGC response since 
> you have a single led that flashes as opposed to a meter, but if your 
> Orion is not too far away from your antenna(s) and/or (especially) if 
> you have reports of tx audio distortion which may only be on amplitude 
> peaks you may very well be experiencing excessive AGC resulting from 
> rf feedback.
>
> In any event, you paid for a 100 watt rig; not a 50 or 70 watt rig so 
> you are entitled to get what you paid for.  Should you verify that it 
> is indeed not putting out 100 w. pep, I hope this helps you solve the 
> problem.
>
> 73,
> rob / k5uj
>
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