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1 hour ago, dgrant said:

I have both the EDM and a C50Z. I got the EDM first so that I could use the radio data feature. When I bought the C50Z as a backup, one season I tried it and got clearer reception than with the EDM. No clue why and I don't have an SWR meter. LOL, I should send it to Jim as he's one of the experts on Radio.

I'd check your power switch inside the EDM.

It has a low and high power setting, I think high power is 500mw although (I could be wrong about that). And low power is either 10mw or 100mw. Can't remember.


As for SWR it shouldn't make that much of a difference on such a low power level. I was more referring to SWR in regards to reflected power when using 7 watts on a rubber duck antenna.

Having that much power going through a rubber duck would likely have a fair bit of reflected power that would heat up and cook the transmitter over time.

But for anything under 3w I don't think it should matter all that much.

So using a rubber duck or even a wire with an EDM or CZH-05B shouldn't matter, however it will effect how far you are able to transmit

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High and low on the EDM is (as I recall) 100 and 10 mWatt

SWR and power have no relationship.

Commercial two way radio users and Hams have been using 3 - 7 watt transmitters with rubber ducky antennas for decades.  Works as well as can be expected for a crappy antenna.

SWR tolerance depends on the design of the transmitter.  The CZH05b and CZE05b transmitters have no protection and the docs say that transmitting into no antenna will instantly kill the final RF amplifier.  The EDM docs says that it can take an infinite SWR without damage.  Take both of those for whatever they are worth.


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7 minutes ago, dgrant said:

I do use a rubber duck antenna but it was made for 2M ham

That is not the best (optimum 1/4 wave for the 88-108MHz range). Each driven, radiating element should be tuned to the frequency it is operated at.  A whip (ducky) is a 1/4 wave. (the ground plane is the other 1/4 wave of the Dipole) .  An SWR meter, is a tool to help you adjust the 'electrical length' so that all the RF gets to the antenna.  A old VHF rooftop antenna, would also direct more of the power to the front.  FM band is between the old Ch6 and Ch 7

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