I am hoping someone here can guide me to what the heck is wrong with
my antenna system. Here is what is going on. Frist, I know neight of
trhese antennas are very good phtsically or functionally BUT they both
can be tuned down to a very accepatble SWR. However, using eithe my
Icom 706 G OR my old Kenwood 440 AT even with a good SWR 1.5 or
better I get a terrible audio report. I have monitored the audio using
the other radio and it sounds like a warble variable picth sounds as I
speak. sounds like very high over driving but I have that all turned
down. I have used an MFJ 949e tuner and even let the Kenwood with
auto tuner tune the antenna same results .. good SWR but terrible
audio. At first I assumed it was the icom 706 but the kenwood sounds
exactly the same. BUT when I do tune on the Kenwood auto tuners it
does seem better... at times...
The radioas are between two computers and I also have a echostation
interface very close with the serial cable connected to the Icom.. I
have tried all combos I can thik of removing and or changing all
connection scables etc.. .. do you think even though the antennas tune
ok and I know they are not the best (that i could be getting some
type of werid resonating? One antenna is a ground mounted vertical the
other is a mulit band trapped diploes I kinds suspect both (since they
are very old) have bed traps etc BUT I still go back to they seem to
tune down in SWR.. help.. it is driving me nuts,, (shirt drive)

thanks any and all ideas are appreciated...

On Thu, 27 May 2004 23:03:31 -0600, Dan wrote:

they seem to
tune down in SWR.. help.. it is driving me nuts,, (shirt drive)

thanks any and all ideas are appreciated...

Hi Dan,

Tune ONE antenna to lowest SWR;
Change the length of the transmission line;
Does the SWR change?
Yes - you have common mode problems
No - you need a paddle for your canoe

73's
Richard Clark, KB7QHC

p.s. What is a shirt drive?

On Fri, 28 May 2004 06:13:15 GMT, Richard Clark
wrotd:

On Thu, 27 May 2004 23:03:31 -0600, Dan wrote:

they seem to
tune down in SWR.. help.. it is driving me nuts,, (shirt drive)

thanks any and all ideas are appreciated...

Hi Dan,

Tune ONE antenna to lowest SWR;
Change the length of the transmission line;
Does the SWR change?
Yes - you have common mode problems
No - you need a paddle for your canoe

73's
Richard Clark, KB7QHC

p.s. What is a shirt drive?

Richard,
thanks for the reply first "shirt drive" is because I either can not
type or cannot read what I type should be "short drive" ..
anyway , what is "common mode problems? not sure I understand ??
tnx

Dan,
If what you describe as a 'warbling' audio is what I
think it is, it isn't the antenna that's a problem, but
the power supply. Sounds like you're running the power
supply beyond it's capabilities. Drawing too much
current, the voltage 'sags', and causes a 'warbling'
audio, no matter which radio you use (unless both radios
have exactly the same 'problem', which is unlikely). I
guess it's possible, but antennas have very little affect
on transmitter audio.
'Doc

Why not use a dummy load and get the antenna and interface cables out of the
equation?
If the problem persists, may be a power supply problem -- filtering or
inadequate current handling.
Check the DX power supply with an Oscilloscope - Turn down the power and
test again.

--
Keyboard In The Noise

Opinions are the cheapest commodities in the world. Author unknown but
"right on"

------------------------------------------------------
"Dan" wrote in message
...
I am hoping someone here can guide me to what the heck is wrong with
my antenna system. Here is what is going on. Frist, I know neight of
trhese antennas are very good phtsically or functionally BUT they both
can be tuned down to a very accepatble SWR. However, using eithe my
Icom 706 G OR my old Kenwood 440 AT even with a good SWR 1.5 or
better I get a terrible audio report. I have monitored the audio using
the other radio and it sounds like a warble variable picth sounds as I
speak. sounds like very high over driving but I have that all turned
down. I have used an MFJ 949e tuner and even let the Kenwood with
auto tuner tune the antenna same results .. good SWR but terrible
audio. At first I assumed it was the icom 706 but the kenwood sounds
exactly the same. BUT when I do tune on the Kenwood auto tuners it
does seem better... at times...
The radioas are between two computers and I also have a echostation
interface very close with the serial cable connected to the Icom.. I
have tried all combos I can thik of removing and or changing all
connection scables etc.. .. do you think even though the antennas tune
ok and I know they are not the best (that i could be getting some
type of werid resonating? One antenna is a ground mounted vertical the
other is a mulit band trapped diploes I kinds suspect both (since they
are very old) have bed traps etc BUT I still go back to they seem to
tune down in SWR.. help.. it is driving me nuts,, (shirt drive)

thanks any and all ideas are appreciated...

Dan,
If what you describe as a 'warbling' audio is what I
think it is, it isn't the antenna that's a problem, but
the power supply. Sounds like you're running the power
supply beyond it's capabilities. Drawing too much
current, the voltage 'sags', and causes a 'warbling'
audio, no matter which radio you use (unless both radios
have exactly the same 'problem', which is unlikely). I
guess it's possible, but antennas have very little affect
on transmitter audio.
'Doc

I agree. You'll hear plenty of stations with warbly audio come this Field Day !

I'd think that with SWR problems, you'd have low power output, but the audio
would be okay.

jw
K9RZZ

On Fri, 28 May 2004 01:33:22 -0600, Dan wrote:
Richard,
thanks for the reply first "shirt drive" is because I either can not
type or cannot read what I type should be "short drive" ..
anyway , what is "common mode problems? not sure I understand ??
tnx

Hi Dan,

When the SWR changes, this is evidence of common mode currents on the
outside of the braid of the coax going to the antenna.

This is a problem because it indicates power is returning to your
transmitter and mixing with other functions (poor shielding). The
garble you describe "could" be due to this, and the test of
lengthening the coax lead to see if SWR changes would verify common
modality. It is a very simple test with a very simple result: the SWR
changes or it doesn't (it shouldn't in a well designed system).

73's
Richard Clark, KB7QHC