[TenTec] Omni VII first impressions....odd things i.e. SWR values

[Mike Bryce]

bob and all..

Here's the set up once again

Radio running from a 14.0 volt supply
one coax cable from the Omni VII to a bird wattmeter with correct slug.
a second coax cable to a 50 Ohm dummy load

Dummy load is within specifications

Press "tune"

Omni VII goes into low transmit

SWR meter shows 9:9 to 1

Bird wattmeter shows NO reflected power (ok, the meter's needle moves  
upward the width of the needle)


Press "tune"

Omni VII goes into low transmit

SWR meter shows 4.5 to 1

Bird wattmeter shows NO reflected power

Press "Tune"

Omni VII shows 2:1 to 1

Bird wattmeter shows NO reflected power

Press "Tune"
Omni VII shows 9.9 to 1

Bird wattmeter shows NO reflected power

Press "tune"

Omni VII shows 1.1 to 1

Bird wattmeter shows NO reflected power


same problem with either antenna port
NO internal antenna tuner installed

Same problem on all bands

I could keep going but I hope you see what I am talking about

The problem is NOT a coax connector or bad cable, the bird would have  
shown that.

I'll have to give TT a call after the holidays..


Mike, WB8VGE
SunLight Energy Systems
The Heathkit Shop
http://www.theheathkitshop.com/
J e e p
o|||||||o
Note: No trees were killed in the sending of this message, but a  
large number of electrons were terribly inconvenienced


On Dec 21, 2007, at 9:27 PM, Bob McGraw - K4TAX wrote:

Would be interested to know what the output power is doing both with the
internal meter and with a external meter when this event occurs.    
Does it
behave the same way with ANT 1 and ANT 2?  I trust that you have the  
AUTO
TUNER off.  This would aid in identifying the area of concern.

Again the way this internal meter system works, it is sampled and  
displayed
via digital processing loop.  Thus, due to time vs. calculation  
differences,
using anything other than a solid carrier I would consider as non-valid.
Also, I suggest connecting the radio with a known good jumper to the
external meter, a known good jumper to a known good dummy load.  And I'd
check it on different bands.  If the problem persists, I'd contact  
Paul at
Tentec Service.

At he same time, I tried my radio on CW, 20 WPM, with the dummy  
load.  The
internal SWR indication was 2.4:1 when with carrier it shows 1.0:1.   
I also
noted that on various bands, in CW at 20 WPM, the SWR was different from
band to band with higher values SWR on 15M, 12M & 10M than on 160M,  
80M &
40M.  In all cases, solid carrier TUNE/PWR shows 1.0:1 on all bands  
and the
external power meter shows 0 reflected watts.

I just went through this exercise with my Omni VII.  Using the internal
meter, in TUNE output power indicated 20W, press PWR and it reads 100  
watts.
I did this 10 times with identical results.  Then changed the meter  
to SWR
and perfumed the same test sequence.  SWR indicted 1.0:1 at both power
levels, 20 watts TUNE and 100 watts PWR

I then switched the 238 tuner inline between the load and the Bird 43P.
Adjusted the tuner for 0 watts reflected on the Bird.  The Tentec SWR
indication was 1.0:1.  I then changed the C value in the 238 tuner to  
show
about 4 watts reflected {had to change slugs to read this low}which  
should
have been a SWR of about  1.6:1.  The Tentec SWR indicated 1.4:1.  At a
different SWR value being 100 watts forward and 10 watts reflected on  
the
Bird, thus from the chart a SWR of 2.0:1 the Tentec SWR indication  
was 2.1 :
1.  Darn close I'd say.

The Bird 43 P with a 250 watt element shows some 18 watts in TUNE and 90
watts in PWR on 75M.  The load on the Bird meter is a 50.5 ohm Bird  
load.
My Omni VII produces some 90 watts on 75M and a gradual decrease per  
band to
80 watts on 10 meters.  The Vcc is 14 volts at the power supply and  
likely a
few tenths less at the radio with the supplied Tentec full length power
cable.  I also noted that the supply amp meter indicated 19 amps for 90
watts output on 75M and 22 amps for 80 watts on 10 meters.  For what  
ever
that's worth.

73
Bob, K4TAX