Hi, Rick
Has anyone converted the Johnson KW Matchbox to an 'Alfred Annecke' style
matchbox? I have a KW Matchbox and you are absolutely right. Works great
on 80 and 40 feeding a 80 meter dipole with home brew open wire feeders.
But most difficult to match anything higher that 40 meters.
Dave WN5V
-----Original Message-----
From: tentec-bounces@contesting.com [mailto:tentec-bounces@contesting.com]
On Behalf Of Rick - DJ0IP / NJ0IP
Sent: Thursday, December 01, 2011 9:47 AM
To: 'Discussion of Ten-Tec Equipment'
Subject: Re: [TenTec] Jupiter Autotuner upgrade?
Frank,
I did begin with "back in the pre-historic days".
What you are calling a deceptive spec was actually the law.
It is how the FCC defined our maximum power.
It is how everybody measured back then because nobody I knew even had a watt
meter.
(could not afford one)
All we had was a volt meter and a current meter.
To comply with the law, you had to measure, or rather calculate your input
power.
All manufacturers specified their equipment in Input Power.
Your KW Johnson Viking Matchbox was not specified for 1KW output in SSB.
It was specified for 1KW Input Power on AM.
When MFJ came onto the scene, they used this same system and it was
perfectly alright back then.
The world changed.
The FCC changed the rules and specified our power limit as 1500w output
power, and affordable watt meters became available.
Most manufacturers changed their method of specifying power.
MFJ did not. And that is the cause of the confusion.
I can't say if it was intentional or simply negligence.
In any case they sure fooled a lot of people into buying their products.
The old Johnson Viking, even in the KW version, is no longer adequate as a
general purpose, "match everything" matchbox.
It's matching range to 50 Ohms is not wide enough.
If you need one or two bands, it's fantastic.
If you need to match a lot of bands, you will probably be disappointed.
If you happen to have an antenna and it does match on 7 or 8 bands with the
Viking, then you are very lucky.
The problem is, it was designed when we had 3 fewer bands (no WARC) and
transmitters had tubes with Pi filters in the output. You didn't have to
match to 50 Ohms. If you put up an 80m dipole today and feed it with
openwire feedline, and then try to match it on 8 bands, you will most likely
fail or forever be trying various lengths of additional feedline.
This problem was recognized and alleviated by a German ham about 35 years
ago, Alfred Annecke.
He brought out a circuit which was identical to Viking on the output side,
but added several more taps on the input side, as well as an additional, 3rd
variable capacitor. His box really could match everything in the "new
days", just as the Viking matched everything in the "old days".
Unfortunately he is now an SK and his products are getting harder and harder
to find. L.B. Cebik, W4RNL (SK) also explained the above in his excellent
article on Link Couplers.
Again, we all have to be on the same page here: I am talking about a
matchbox for the person who only has one antenna and wants to be QRV on
every HF band there is. If you are only trying to get a good match on one
or two bands, of course tweaking the antenna is the better solution.
73
Rick, DJ0IP
-----Original Message-----
From: tentec-bounces@contesting.com [mailto:tentec-bounces@contesting.com]
On Behalf Of Frank
Sent: Thursday, December 01, 2011 3:33 PM
To: Discussion of Ten-Tec Equipment
Subject: Re: [TenTec] Jupiter Autotuner upgrade?
Rick - DJ0IP / NJ0IP wrote:
>As a rule of thumb for estimating, it simply to take 50%.
>A 1500w MFJ Matchbox rated for the old SSB rating system is really a 750w
>matchbox.
>Their 3000w Matchbox can handle 1500w if the SWR does not get too high.
>
>
That sort of specmanship is troubling. Depending on what is 'too high'
with regards to SWR. Most folk don't need a matchbox unless their SWR
IS too high. A matchbox that cannot handle 'high' SWR is a useless
appliance. In fact, if the requirement for 'low' SWR is low enough, a
little tweaking of the antenna might be in order making the light duty
matchbox unecessary.
The most deceptive amplifier power spec that I can remember is one
claiming 1KW PEP INPUT. I guess they were hoping the buyer would
confuse that with a 1kw amp. One of the best ways to judge an amp is to
look at what it is using for finals. The same goes for matchboxes
except now we are looking for capacitor voltage ratings and/or plate
spacing.
For my money I will stick with my old Johnson KW matchbox.
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