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CYBER MAX 15/SWR meter/Antenna tuning

 
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CYBER MAX 15/SWR meter/Antenna tuning
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NISEMUSIC
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Post CYBER MAX 15/SWR meter/Antenna tuning Reply with quote
Hi,

I'm about to purchase the Cyber max 15w and Comet antenna combo but am unsure whether to buy a SWR meter with it and would appreciate some advise from the experts.

I've checked out the specs, FAQ's and other users experiences, all of which lead me to believe that I do not need a SWR meter. The most conclusive data I can find is on the Comet's spec page where it says that it is "fully wideband - no tuning necessary." Since no tuning is necessary, I think that there should be no SWR issues and thus, no need for an SWR meter. Is that correct?

Even if the Comet does not need to be tuned when used with the Cyber Max 15W and I do not need a SWR meter, I would like to understand antenna tuning a bit more. How do you correct SWR problems?

Thanks for your help everyone!
Sat Jan 21, 2006 12:18 am View user's profile Send private message Visit poster's website
Sir Nigel
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Post Reply with quote
The Comet has to be tuned, preferably with an SWR meter. There are two antennas that don't require tuning, but they are directional.

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Sat Jan 21, 2006 1:15 am View user's profile Send private message Visit poster's website
NISEMUSIC
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Thanks for your quick reply Sir Nigel. I was kind of expecting the answer you gave and did some more research into the subject. I think I've figured out the correct tuning procedure...

Am I correct in thinking that the comet antenna is tuned by extending or retracting the various parts, much the same way that traditional rabbit ears are adjusted?

If that is the case then I think a SWR meter would be essential to obtain an optimal SWR ratio?

Another question that arose in my research deals with dummy loads. My understanding is that you need a termination point when operating a transmitter to avoid damaging the unit. That termination point can either be an antenna or a dummy load. If I am correct thus far, am I also correct in thinking that I WOULD need a dummy load to tune the Cyber Max 15W without stomping on other broadcasters frequencies or damaging the Cyber Max?

Thanks everyone for your patience and help with my Transmitting 101 questions!
Sat Jan 21, 2006 4:33 am View user's profile Send private message Visit poster's website
Sir Nigel
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Yes, to get the optimal ratio you would need the meter. I know that the chart that comes with the antenna for tuning should only be viewed as a basic guide as it was rather inaccurate when I was tuning my antenna.

I'm not sure about a dummy load, but you can at least use your potentiometer to reduce your output so that you hardly interfere when tuning.

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Sat Jan 21, 2006 5:07 am View user's profile Send private message Visit poster's website
NISEMUSIC
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Post Reply with quote
Thanks Nigel!

I guess I'll be picking up a SWR meter with everything else then.

Does anyone else have and thoughts on the Dummy load issue?

Thanks!
Sun Jan 22, 2006 1:31 am View user's profile Send private message Visit poster's website
cliffyk
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The absolute need for a dummy load depends upon the final RF design (and yes, you can fry the output without one on some designs). However you won't be able to do any useful tuning of the exciter without one, and it's also one of those "you want to do it correctly?" issues.

I bought one of these from eBay six months ago, from this same seller (he says he has "lots of them". It is very nice, will handle 62.5W, and has an attenuated tap that's handy for monitoring the waveform via a 'scope, spectrum analyzer, or counter--and best of all it's only $22 with shipping to any US destination.

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Sun Jan 22, 2006 3:21 am View user's profile Send private message Visit poster's website
pcs
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Post Reply with quote
If you can adjust your power, you may get away without
a dummy load. How?

1.) Easy, set transmitter to say 1W.
2.) This is a low enough power level for the 15W final stage
to handle easily.
3.) Now tune your antenna. Set power to full 15W.

But dummy load is really usefull for tuning and testing the amplifiers
and transmitters and it is nice to have one handy.

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Sun Jan 22, 2006 2:39 pm View user's profile Send private message Visit poster's website
NISEMUSIC
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Post Reply with quote
Great, thanks a lot for your replies. You all have been very helpful!

I'm sure I'll be posting again soon once I purchase and begin testing my new gear but eventually I hope to be able to provide some answers instead of only questions. Before then, I do have one more question about dummy loads...

With a dummy load attached to the output, the RF is dissapated into heat so that you can tune a transmitter without interferring with other frequencies.

There still must be some RF being transmitted from the rig though so that I can pick up and test my signal with a radio tuner. Where is this coming from and how strong a signal is being output?
Sun Jan 22, 2006 3:46 pm View user's profile Send private message Visit poster's website
pcs
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There is some signal left, certainly enough to be picked up
by nearby radio receiver, but probably won't make it more
than 50-100m far.

This is the inefficiency of the case, which lets some rf out, and
the connectors, dummy load and probably in most cases power
supply cable and audio cable that radiates a minimal amount of RF.

Think of it as a fish tank with tiny holes here and there, with a small
amount of water dripping out.

Nothing to worry about unless you're running killowats.

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Sun Jan 22, 2006 3:55 pm View user's profile Send private message Visit poster's website
cliffyk
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Although resistive dummy loads are properly described as "dissapative non-radiating devices", the practical reality is that if you feed enough RF power into nearly anything it will radiate some of that power. It may not radiate much, however it will radiate some...given sufficient input you could probably get a roll of paper towels to radiate a useful FM signal.

When I connect the 7W output of my Max Pro I to the Celwave dummy load I described in my previous post I can receive a reasonably clean stereo signal through most of my house (1800 sq. ft.), and a very clean signal on my NAD 4300 tuner with on of those Terk indoor amplified antennas. This tuner is located in living space about 45 feet from my workshop, on 'tother side of two sheetrock/frame walls.

I.e. the signal is quite useful for "on-the-air" monitoring.

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Sun Jan 22, 2006 4:12 pm View user's profile Send private message Visit poster's website
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Post Reply with quote
Mark,

GREAT analogy...

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