[TenTec] OT: Question to the group

Mon Jul 18 10:45:53 EDT 2016

Great response Rick! 

I think it would be hard for me to come up with a photo of my Siamese dipole though… ASPCA and all...

73

Gary

> On Jul 18, 2016, at 9:14 AM, rick at dj0ip.de <Rick at dj0ip.de> wrote:
> 
> Hi Gary,
> 
> I found time to come back in and continue addressing more of the points.
> 
> Nothing is wrong with the resonant antenna.  It is what I have used quite a lot over the years.
> We are on the same page here. However it is wrong to believe that only resonant antennas can be efficient.  Maxwell clearly points that out, as does Cevik.
> 
> I was only saying that people often are forced to use non-resonant antennas due to space limitations and that the JVM (in standard format) is not the best matchbox for that.  
> 
> I was in full concert with you on all points, except ... and maybe it wasn’t even you who said it . . . it was claimed several times that the JVM was the greatest matchbox ever.  It was great in its days, but had weaknesses later as we got more bands and people began to match funny things with them.  At least one company (Annecke) improved on the design and sold them.  It was distinctively better.
> 
> But wait, W6SAI published an article showing how to do that, something like 50 years ago.  That's where I "borrowed" the idea, then applied it to the JVM and improved it and published instructions on how to d-i-y. 
> 
> I went to great length to explain and show people how to remedy this and many people have applied my mod to their JVM.  I continue to get thank you emails for the work from people who have successfully done the mod.
> 
> I am a firm believer in link coupler matchboxes and have a couple of pages on my web showing people how to build their own simple, dirt cheap link coupled matchbox.  But I have altogether 4 different circuits for 4 different applications. 
> Each fits a different set of circumstances where it works, but it fails everywhere else.  It is difficult to put them all in one box and the high power switch would cost a small fortune.  So I make different proposals for people confronted with different tough environmental situations . . .  such as how to get a relatively efficient power transfer into a short 20m (66 ft.) long (or even shorter) dipole on 160m.  
> 
> I love quads and loops much more than dipoles. 
> I began feeding them with open wire back in the 1970s, using the Annecke Symmetrical Coupler, which was the matchbox that is an improvement over the JVM.  Except mine was home-brew using spare parts I purchased directly from Annecke. 
> 
> HOWEVER THE FACT REMAINS:  THERE AREN'T ENOUGH JVM's to go around if everyone wants one.
> Even if you are lucky enough to find one, you often find them "melted" on the inside.
> Therefore some kind of alternative is required.
> 
> A much less quality but very practical solution is to use a good 1:1 Guanella balun between a simple L-Network and the openwire.  That's "1:1, not "4:1".  
> I often use the Model 238 like this.
> Especially with low power (100w or less), this can be a good substitute.  
> 
> In my 45 years of living on this side of the pond, I have never once seen a JVM for sale on the used market.  The ANNECKE I speak of was great, but Alfred Annecke built and sold exactly 20 units.  I built my own.  So there are perhaps 21 units floating around somewhere in the world. Won't find one of those either.  So most people must seek or build something else.
> 
> Now to your two cats and the JVM.
> I built something similar using two galvanized trash cans.
> You can find a picture here: 
> http://www.dj0ip.de/antennas/ 
> Pictured is one version which I fed with a short coax.
> 
> I'll put that up against your Siamese cats any day! (hi)
> 
> Cheers Gary!
> 
> 73
> Rick, DJ0IP
> 
> 
> -----Original Message-----
> From: TenTec [mailto:tentec-bounces at contesting.com] On Behalf Of Gary J FollettDukes HiFi
> Sent: Monday, July 18, 2016 9:42 AM
> To: Discussion of Ten-Tec Equipment
> Subject: Re: [TenTec] OT: Question to the group
> 
> 
> 
>>> Stating individual cases where something worked proves nothing.
> 
> Well, actually it does. As I pointed out, with a RESONANT cubical quad, driven with 470 Ohm Dentron parallel line, I got a perfect match on 20, 15 and 10. This was an efficient antenna with efficient feed lines and an efficient (in this application) tuner. It was positioned quite a long distance from the transmitter so the lower loss parallel feeling was of some advantage.
> 
> Better would have been the use low loss ceramic spacers and true parallel ladder line. However, the Johnson matchbox would have worked equally well in that application, whereas the autotuners and most of the T match tuners wouldn’t have worked at all without an external BALUN.
> 
> Since my radio at the time, a Drake TR7, had pretty good low pass filters within, I was not too concerned that the Matchbox offered no such lowpass filtering.
> 
> Even more important than the match is the near-perfect balance of currents on the line (as you mentioned). Two bad things happen when the currents on “parallel” lines are not balanced. Your noise level on receive goes up since the feedline begins to act as part of the antenna and your chances of getting the Worked All Neighbors award in transmit also goes up dramatically as the feed line begins to radiate where you do not want it to radiate.
> 
> Nothing matches everything. Nothing even works well for everything. Devices like this need to be matched to the application. I only sang the praises of the Johnson because it did indeed work with every application in which I used it.
> 
> Nothing else did as well…
> 
> As I said before, improvement is always welcome and what you discuss in terms of such improvements is great. Why does this become contentious?
> 
> A little humor, if that’s allowed:
> 
> I once got a perfect match with a Johnson Matchbox using two cats as an antenna, with alternately polarized mice as spacers for feed line made of old violin strings (catgut).
> 
> Of course, they were Siamese cats… It was, after all, a balanced dipole…
> 
> April fools...
> 
> 
> Beyond that, what is wrong with resonant antennas? Where is the advantage of a non-resonant antenna? Nikola Tesla clearly showed the inherent advantages of resonant loads 120 years ago… They are pretty easy to match too!
> 
> 
>> On Jul 18, 2016, at 1:09 AM, Gary J FollettDukes HiFi <dukeshifi at comcast.net> wrote:
>> 
>> I’ll just stay with resonant antennas…
>> 
>> Gary
>> 
>> 
>>> On Jul 18, 2016, at 12:48 AM, rick at dj0ip.de <Rick at dj0ip.de> wrote:
>>> 
>>> Stating individual cases where something worked proves nothing.
>>> I've had half a dozen cases where it did not work and other matchboxes did.
>>> 
>>> In order to gain clarity on this, you must try it with all kinds of 
>>> antennas; resonant antennas, long antennas, short antennas, odd sized 
>>> loops, etc.
>>> 
>>> What the Johnson does well is push equal amounts of current into both 
>>> wires of the feedline with relatively high efficience, if and only if 
>>> it finds a match.
>>> What it does poor is match over a very broad matching range.
>>> 
>>> You don't have to trust me; try it as I have and compare it to an 
>>> MFJ-974 or MHF-976.
>>> 
>>> OR... simply read the ARRL test report where the ARRL shows several 
>>> balanced matchboxes and their matching ranges, including the JVM.
>>> 
>>> Now I guess I have to go research the issue it was printed in because 
>>> it's probably too much work for some of the readers.
>>>> "A New Generation of Balanced Antenna Tuners", by Joel Hallas, W1ZR, 
>>>> QST
>>> September 2004. 
>>> 
>>> OR, simply do what I have said her MANY TIMES, go to my web site, 
>>> find the page on MATCHBOX-SHOOTOUT And read the page, plus download 
>>> the file at the bottom of the page.
>>> THERE you will find a nice colorful Excel spreadsheet comparing the 
>>> matching range of the various matchboxes.
>>> THERE you will see that the JVM was indeed limited in matching range.
>>> 
>>> THEN go read my web page on how to fix it.
>>> 
>>> AND THEN YOU WILL HAVE THE BEST MATCHBOX EVER!  ;-)
>>> 
>>> 73
>>> Rick, DJ0IP
>>> 
>>> 
>>> -----Original Message-----
>>> From: TenTec [mailto:tentec-bounces at contesting.com] On Behalf Of 
>>> Carter
>>> Sent: Saturday, July 16, 2016 9:32 PM
>>> To: tentec at contesting.com
>>> Subject: Re: [TenTec] OT: Question to the group
>>> 
>>> On 7/16/2016 10:13 AM, Carter wrote:
>>>> On 7/15/2016 6:59 PM, Jim Allen wrote:
>>>> 
>>>>> I had one of those [135 foot dipole fed with ladder line], not at  
>>>>>> 60', about half that.  CC&Rs and all that.
>>>> 
>>>> The exact setup I've got, also at 30 feet.
>>>> 
>>>>> What is a "well designed truly balanced antenna tuner?"  From what  
>>>>>> I've read, there aren't many.
>>>> 
>>>> Johnson Matchbox, kW or 275 watt version, not "perfection" but 
>>>> certainly very good -- and readily available at a fairly modest price.
>>>> 
>>>> Just my 2 cents...
>>>> 
>>>> Carter   K8VT
>>>> 
>>> 
>>> Sorry, forgot to mention it earlier...
>>> 
>>> Not to say my Johnson kW matchbox is the "best ever"; however, it 
>>> works flawlessly  with my FT1000MP and 135 foot ladder line fed 
>>> dipole on ALL (including WARC) bands. Worst case is 2.1:1 on 30 
>>> meters, all other bands 1:1.
>>> 
>>> Carter   K8VT
>>> 
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