[Elecraft] Sherwood's receiver performance table updated

Wed Apr 27 14:15:41 EDT 2016

Ken - I thought my "note"/reply was focused on long runs with low SWR (as in, for instance, a 120' run of LMR-400 with an auto tuner at the base of the vertical or whatever antenna)......

Let's leave radial/ground shield and counterpoise discussion for another time....smiling!!

71.5/72 Jimm R.

________________________________
From: Ken K6MR <k6mr at outlook.com>
Sent: Wednesday, April 27, 2016 12:10 PM
To: James Rodenkirch; elecraft at mailman.qth.net
Subject: RE: [Elecraft] Sherwood's receiver performance table updated

No problem. Yes, open wire line has its own problems. I was reacting to your note regarding using short runs of coax operated at high SWR. There is nothing inherently inefficient about doing so. Like any design it’s easy to run the numbers to determine what the actual losses are. Many times they are just too small to worry about. Especially in the case of verticals, the ground losses will be far higher unless you invest in an excellent radial/ground shield underneath it. The tuner can’t help that.

Ken K6MR

From: James Rodenkirch<mailto:Rodenkirch_LLC at msn.com>
Sent: Wednesday, April 27, 2016 11:01
To: Ken K6MR<mailto:k6mr at outlook.com>; elecraft at mailman.qth.net<mailto:elecraft at mailman.qth.net>
Subject: Re: [Elecraft] Sherwood's receiver performance table updated

Did not mean to sound argumentative, Ken.....apologize if it came out that way....I am "involved" in this discussion becuz' of Don's initial post about new hams not understanding the advantageous aspects of open wire feed line....

________________________________
From: James Rodenkirch
Sent: Wednesday, April 27, 2016 10:38 AM
To: Ken K6MR; elecraft at mailman.qth.net
Subject: Re: [Elecraft] Sherwood's receiver performance table updated

It is not "the principle behind the use of open  wire feed line," Ken IF, I place an antenna auto tuner at the base of, for instance, a vertical and feed the tuner with low loss coax....

I understand the use of open wire feed line and an ATU prior to attaching to the xmtr....BUT...see above - works as well, if not better 'cuz I don't have to worry about the open wire feed line running too close to metal objects...

________________________________
From: Ken K6MR <k6mr at outlook.com>
Sent: Wednesday, April 27, 2016 9:36 AM
To: Jim Rodenkirch; elecraft at mailman.qth.net
Subject: RE: [Elecraft] Sherwood's receiver performance table updated

“P.S. I don't subscribe to the notion that quality coax runs of < 150 feet
make it "ok" to have the ATU in the shack while operating an antenna on
multiple bands....what technical evidence of that posit do you have to
share????”

Jim:

Google “transmission line bounce diagram”. This is a simple concept easily proven by mathematics.

On a practical level, this is the concept behind the use of open wire feed lines. It’s been done for decades. The type of feed line does not change the theory.

Ken K6MR

From: Jim Rodenkirch<mailto:rodenkirch_llc at msn.com>
Sent: Wednesday, April 27, 2016 06:21
To: elecraft at mailman.qth.net<mailto:elecraft at mailman.qth.net>
Subject: Re: [Elecraft] Sherwood's receiver performance table updated

"It all depends" is/was the premise for my reply, Don.

 If new and old hams don't understand the potential problems with long runs
of coax to/from an antenna they want to operate on multiple bands and an ATU
in the shack they will be surprised at how inefficient their system is.

P.S. I don't subscribe to the notion that quality coax runs of < 150 feet
make it "ok" to have the ATU in the shack while operating an antenna on
multiple bands....what technical evidence of that posit do you have to
share????

Note 1: I had a 43' vertical with top loading wires in a NORD-style config
with my external ATU at the base of the vertical and 120' of coax back to
the shack ---- never saw a VSWR delta of more than .2 between what was
"seen" at the input to the tuner and what was "seen" at the xmtr while
operating on 160 through 20 meters.

--
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