[TenTec] Slightly OT

[Art Trampler]

Hi Gang,

 

This is an antenna/impedance transformation device question, but the devices
in question are a Ten-Tec 238B, and the (LDG) internal tuner on a Pegasus.

 

Antenna: 140’ sloping dipole, apex at 45 feet in a tree, ends around 28’. It
is fed with 10’ of LMR600 to a 4:1 current balun, and from that point with
about 100’ of near-600 ohm ladder line (4” spreaders from www.cnc73.com).

 

Symptoms: The internal tuner finds a match on all bands other than 160
(where the whole antenna is ¼ wavelength). With the 238B I cannot match 17,
15, 12 or 10. The best I might see if 4:1, and even then it is very
sensitive, such that any adjustments vary the displayed output in an Autek
WM-1 wattmeter as well as the calculated SWR. Measured output on the Autek
might fall to “0.” I tend to rely on the reverse power setting on the 238B
for tuning, but as SWR falls, so often does the measured output. 

 

The closest match on these bands is found in “bypass” on the 238B.

 

All this was done with 10 to 25 watts output.

 

Knowing that the 238B has a wider tuning range than the internal LDG tuner,
I am a bit perplexed. Could it be poor grounding? Beefing the grounding of
the antenna tuner is one of my next projects. Or could it be stray
inductance within the tuner that I cannot get rid of merely by setting the
inductor all the way counter-clockwise? That is what I tend to believe.

 

Your thoughts? 

 

In other news, all relays replaced on Pegasus and it works fine, and grid
protection circuit for 425 nearly ready to test and drop in.

 

73,

Art K0RO