[TenTec] OMNI-C on 17 meters concern

[K & H Darwin]

So this 1 watt output on 17 meters is only there when the rig is in
transmit mode, right?  If you increase the drive level does the rig work
correctly?  Is this only a problem for QRPp operation or does it affect QRO
operation as well?

Keith Darwin
KD1E
Ferrisburg, VT


----------
> From: Steve Ellington N4LQ <N4LQ@iglou.com>
> To: TenTec@Contesting.com <tentec@contesting.com>
> Subject: [TenTec] OMNI-C on 17 meters concern
> Date: Sunday, March 07, 1999 3:28 PM
> 
> 
> Being concerned about out of band signals on my Omni-C, I have performed
the
> following experiments.
> 
> 1. Connected Omni C to 50 ohm dummy load.
> 
> 2. Connected scope to coax Tee at dummy load.
> 
> 3. Measured voltage at 7, 14 and 18mhz with drive control set for 0.
> 
> Here are the results:
> 
> 1. RMS voltages at 7 and 14 mhz were .35v or .0025 watts
> 2. RMS voltage at 18mhz was 7.07v or 1 watt.
> 
> This indicates that at 18mhz, the Omni C produces 400 times more power
than
> on the other two bands. Now the question is, what frequency is this power
> being generated?
> Not having a spectrum analyzer, I was forced to use crude methods of
> testing.
> 
> 1. Inserted the TenTec 238 antenna tuner between dummy load and Omni C.
> Tuned for
>    best match. Results showed no additional attenuation of the 18mhz
signal
> on the scope.
> 
> >From this, I gathered that if other frequencies were being generated,
some
> attenuation would have be obvious on the scope.
> 
> 2. Using a monitor receiver, IC-706, I measured the signal strength of
the
> Omni C (drive set for zero) at 7, 14 and 18mhz. The signal on 18mhz was
> about 25db stronger than the other two bands.
> 
> Conclusion:
> 
> With the bandswitch set for 18mhz and the drive control fully
> counterclockwise, the Omni C produces 1 watt of power. 10v peak X .707 =
7v
> RMS.  7squared divided by 50 ohms = .999698 watts,
> 
> On other bands the Omni C produces only 2.5mw, making it an excellent
QRPp
> rig for any band except 17 meters where it can become a QRP rig.
> 
> I no longer fear using my Omni C on 17 meters since most if not all
> measurable power is radiated on the correct band.
> 
> 73 Steve N4LQ
> 
> 
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