[TenTec] Jupiter Autotuner upgrade?

Thu Dec 1 05:00:27 PST 2011

BACK in the pre-historic times, when there were no transistors and only
tubes, the US had a power limit of 1000w Input Power.

P=Isq. R,  or  P=E/I were common formulas to use.

Let's take the second one.

We have a linear running 1000v and 500 mA of courrent.
Multiply 1000 x 0.5 =  500w input power

Now let's assume that amp is running in Class C mode.
Class C typically yields about 60% to 65% efficiency.
Let's go with 65%

65% of 500w Input Power = 325 Watts Output Power.

So is this a 500w amp or a 325w amp?   That is Input vs. Output.

BUT, for SSB, we can't run class C (too much distortion).
So we must run perhaps class B.
Class A gets only about 50% efficiency, class B about 55%.
Let's say we were running that amp in class B (ssb).

55% X 500 = 275 watts  (now that 500w input amp is in reality only a 275w
amp if we specify it in output power).

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.

Viola.  Now you know.

73
Rick

-----Original Message-----
From: tentec-bounces at contesting.com [mailto:tentec-bounces at contesting.com]
On Behalf Of Richards
Sent: Thursday, December 01, 2011 12:25 PM
To: Discussion of Ten-Tec Equipment
Subject: Re: [TenTec] Jupiter Autotuner upgrade?

I must admit to not understanding what MFJ means by input power versus 
output power.  I figure output power is what comes out of the amp on the 
way to the antenna, with the tuner in between... OK... but I don't get 
what they mean by "amplifier input power"  - which I have read in the 
catalog descriptions.

It is just this sort of doubletalk that sent me to Palstar for a pair of 
tuners.

My big stick has an 4:1 Un-Un made by DX-Engineering.  It came with a 
4:1 current balun that worked fine (the original balun was a 4:1 
combination current balun and and RF choke design that is supposed to be 
OK, but after Zero-5 was caught peddling the wrong type balun (a voltage 
balun) from ArraySolutions,  then Array Solutions got wise and quickly 
supplied a proper Un-Un.    There was some flap on this on qRZ.com where 
some Dutch ham complained and the guys on the forum figured it out   (He 
re-wired his to the correct configuration and it worked swell after 
that...)   Soon thereafter, DX-Engineering came out with its 4:1 Un-Un. 
    Long story, but I was there all the way, and DX-Engineering 
practically gave me the new design Un-Un because I was fairly prominent 
in promoting the product on various web discussion groups. 
Coincidence ?   Yes, absolutely !

I like the guy at Balun-Designs.   He made the one I use on my OCF 
dipole.   He and I had quite a nice discussion about where to put the 
feed point in order to maximize performance on 15 meters, and lower 
overall impedance to around 200 ohms  (referencing our previous 
discussion thereon.)

I agree that, if I were to try one of these newer MFJ tuners, I would 
probably pick the legal limit model, and then only run about 500 - 600 
watts at most, keeping everything conservative.  I don't like to stress 
the amp, either.  It is not worth it, and does not really get you any 
more S-meter units.

=========================  JHR  ================================

On 11/30/2011 9:53 PM, Rick - DJ0IP / NJ0IP wrote:
> What James, a Chinese product with quality issues?
> Are you serious?
> ;-)
>
> Now I'll be serious and say that the CG-2000 which is the low power
version
> MFJ is re-badging, in the meantime is shipping at a pretty good quality
> level.  It wasn't always. That of course is no assurance that the bigger
> versions will have no quality issues.  In fact my experience, having
worked
> with the Chinese a lot is that you have serious quality issues with every
> new product, much more so than we know it with new products made in our
own
> countries.
>
> Also, as Geoff pointed out earlier, these power ratings of 1500 and 600
are
> misleading and possibly bogus.
> Besides being subject to the same rules of all matchboxes, "when the SWR
is
> higher, you have to reduce power", we also need to understand if these new
> boxes are still rated with the "old" MFJ rating system of "SSB Input
Power".
> If so, then you can halve those power ratings immediately before you even
> unpack it.  A straight forward question to MFJ tech support should get an
> answer to this, if you can get an answer from them.
>
> My hunch is that this unit is actually rated in output power because
that's
> how the CG-2000 and CG-3000 are rated.
> Just don't forget the bit about reducing power when the SWR is high.
>
> Now in its manual it says:
>
> Features
> . Automatically matches antennas from 12 to 1600 ohms impedance (SWR up to
> 32:1)
> . Handles 1500 watts SSB/CW
>
> Here it does not specify whether it is Input Power or Output Power.
> In the specifications section it is also vague.
> Unfortunately there is no schematic, so I could not see the voltage
ratings
> on the capacitors.
>
> The matchbox is rated to an SWR of 32:1, or 1600 Ohms.
>
> There is a long paragraph explaining how to add additional feedline
lengths
> when you get impedances which cannot be matched.  Same as in every other
> matchbox's manual.
>
> So James, I guess the big question is, will your big stick present an
> impedance on any band which is above 1600 Ohms?
> I would suggest using a 4:1 Unun (I sourced one from Balun Desgins just
for
> this purpose).  If you have a good 4:1 balun, you only have to re-solder
one
> wire and it's an Unun.
> You may find that you have to switch the unun out on some bands,
especially
> the low bands.
>
> Finally, being as you only run 600w anyway, you shouldn't have a problem
> with it, especially if you use an Unun where required.
>
> 73
> Rick
>
> -----Original Message-----
> From: tentec-bounces at contesting.com [mailto:tentec-bounces at contesting.com]
> On Behalf Of Richards
> Sent: Thursday, December 01, 2011 1:20 AM
> To: Clayton Brantley; Discussion of Ten-Tec Equipment
> Subject: Re: [TenTec] Jupiter Autotuner upgrade?
>
> MFJ has a new remote auto tuner that costs about  $750 - supposed to
> handle 1500 watts.   They have one that handles 600 watts for $400.
>
> Some of use with 43 foot monopole vertical antennas are waiting to see
> how the first user reviews look before we dive into an MFJ product.  I
> suspect they are made by the same Chinese outfit that made similar
> tuners formerly sold by  Array Solutions -  but Jay Terleski the owner
> said they dropped the line over quality control issues.  At that time,
> they had one that could handle 800 watts.   I suspect (hope, actually)
> that if they are from the same manufacturer, they have been improved.
> Time, I suppose, will tell.
>
> ========================== JHR ==============================
>
>
>
>
>>    From: Rick - DJ0IP / NJ0IP<Rick at DJ0IP.de>
>
> I think MFJ recently came out with one that can handle high power,
>> but I haven't seen it yet and don't know how much it costs.
>
>
> ===============================================================
>
>
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