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High SWR out the linear

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Mountain 509
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High SWR out the linear

Post by Mountain 509 » Wednesday, 31 August 2016, 23:52 PM

I hooked up a Elkin Mini-Max 4 tube. PEP is about 380w. When I checked the standing wave with a dead key the reading was 1:1.4 . But when modulating the standing wave climbs up to almost 1:3+ . My RM KLV 400 has a dead key swr reading of 1:1.4 also. but when modulating the standing wave climbs to about 1:2.1 . Is this a problem? Just a note.......All jumpers have been tested and antenna (I-Max) is tune. When running just the radio barefoot through the same jumpers I get a swr reading of 1:1.2 (no increase in SWR during modulation).

P.S> My main concern is... should the Standing Wave be increasing during modulation? Your input would be greatly appreciated. Thank you in advance.. Randall


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Re: High SWR out the linear

Post by jessejamesdallas » Thursday, 01 September 2016, 4:52 AM

Always check SWR with mic gain all the way off...modulating while trying to check just gives you wroth less false readings.
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Re: High SWR out the linear

Post by MDYoungblood » Thursday, 01 September 2016, 9:45 AM

If the SWR is like you say then there isn't a problem, like JJD says, check the SWR with a DK, no modulation. If the meter your using has a wattage setting switch to it, an averaging meter doesn't move the needle much but a PEP meter will show swing.

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Re: High SWR out the linear

Post by Mountain 509 » Thursday, 01 September 2016, 9:46 AM

Thanks for the reply, jessejamesdallas. That is how I check my SWR. I leave the MOD/SWR meter on my Cobra 2000 on the SWR reading and was caught off guard when I saw it swinging into the red while talking on this [new to me] Elkin amp. I just needed some reassurance. Thanks again.....Randall

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Re: High SWR out the linear

Post by MDYoungblood » Thursday, 01 September 2016, 11:35 AM

Since I read your using the radio's SWR meter what does the antenna read without the amp inline?

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Mountain 509
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Re: High SWR out the linear

Post by Mountain 509 » Thursday, 01 September 2016, 11:57 AM

MDYoungblood wrote:Since I read your using the radio's SWR meter what does the antenna read without the amp inline?

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As I stated above without the amp on the Cobra's meter reads a 1:1.2, same as the Dozy meter I have inline. That's with the amp inline and not turned on. The reading is the same if I connect the antenna directly to the radio as well....Randall

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Re: High SWR out the linear

Post by MDYoungblood » Saturday, 03 September 2016, 6:43 AM

Your Elkin amp is one of the nicer amps, using four 12JB6 tubes, basically it's a modulator, have a low DK (around 50w with a 4w drive), has lots of swing wattage (over 250w RMS) and it really shines on SSB. I'd drive it with a lower DK from the radio to save the tubes, they are expensive.

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Re: High SWR out the linear

Post by Mountain 509 » Thursday, 08 September 2016, 21:10 PM

MDYoungblood wrote:Your Elkin amp is one of the nicer amps, using four 12JB6 tubes, basically it's a modulator, have a low DK (around 50w with a 4w drive), has lots of swing wattage (over 250w RMS) and it really shines on SSB. I'd drive it with a lower DK from the radio to save the tubes, they are expensive.

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Greg
Thanks for your reply, Greg. You really were a big help when I first got this base station up and running last Nov. I have come a long way since then. This is my second Elkin Mini-Max. The first one I had lasted about 30 days, then the transformer let go. I actually had to open the windows to let the smoke out! That box was about 35 years old and although it had new tubes installed when I bought it, the transformer was at its life's end. I still have it sitting in the corner and maybe one day I will take it to Ray's and let them fix it. As you may well know it will cost more than it's worth to replace the transformer. I am lucky in that I live about 1 1/2 hour drive from Ray Phelps' shop. He is mostly retired and his son does most of the work now, I believe.

This new (to me) Mini-Max was bought from a local cb'er that used it to drive a HeathKit ,and was recently totally refurbished by Ray's son. A variable was installed and it is a talker. With the variable turned up to max, and a 2.25w deadkey out of my Cobra 2000, it shows a deadkey at 25w swinging to 390w PEP. It shows right at 190W RMS on my Dozy meter. These Elkin amps really are great amps. I know there are a few that don't think much of the sweep tube boxes, but I am a believer, and living here in NC there are quite a few floating around to be had! My RM KLV 400 can not hold a candle to this Elkin, and that KLV is no slouch.....

Thanks again.......Randall (Mountain Top)


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