[TenTec] Transmatches/Tuners/Etc.

[Clark Savage Turner WA3JPG]

Hi Puck!

> Maybe the Ultimate and SPC were not forerunners of the T but I never saw 
> a T until after that Murch Ultimate came out.  Other manufacturers came 

I will ask around, that is a good question.  That is a good way to 
find out.  Anyone know the history of the general cap-tee match?  I
had assumed it predated the Ultimate and SPC since I thought that
both of them touted the bandpass design as desireable over the 
cap-tee high pass response.  I may be mistaken.

> As to harmonic attenuation, that's hardly a concern these days as most 
> rigs are quite adequate in this area.  A PI or series inductor L are both 

Ah!  You don't live here in Irvine for sure.  Hi Hi.  I have quite 
an RF environment here and untuned antennas that are large.

> loss pass in nature and would be better than a T or an Ultimate which are 
> both high pass types. The SPC is basically an Ultimate with that third 
> cap relocated to give more of a band pass rather than high pass effect.

That is just what I need in most cases.  I have very, very strong 
stations on the AM BC band, and other hams local to me.  I have a 
500 foot horizontal loop up in the trees at 50 feet.  Most every radio
I put on there dies under the RF that comes off the coax.  Even 
Kenwood 940's and the OMNI VI crunch to some extent.  

> I'm sure you're right about the PI networks in the old tube rigs.  I just 
> pulled some numbers out of the air.  My DX 20 would load power into 
> everything from a light bulb, to a window screen to a short piece of wire 
> lying on the floor.  It even worked quite well on an off-center fed 
> dipole I had fed with 75 ohm twin lead.

I remember those days of 75 ohm twin lead!  I am sometimes tempted
to just take the pi network components out of my T-60 and build a 
little tuner for myself out of them.  

Actually, I have been thinking of taking my Heath SA 2060 tuner
and making it a pi net tuner by adding more capacitance to the
variables with switches.  Just need to find the QRP Quarterly
article to firm up my own suspicions.  Your points about the L
network are well taken, one less component is pretty much one
less component to dissipate RF :-) .  I have never used the 238
so I have no experience with them.

Clark
WA3JPG

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