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Old 26th Jun 2021, 9:34 am   #21
SiriusHardware
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Default Re: President Lincoln SWR issue "only" when meter inline.

Touché. That's a common typo for me, especially when entering passwords. I wish the zero in computer fonts always had a diagonal line through it, old school.
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Old 26th Jun 2021, 9:04 pm   #22
crackle
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Default Re: President Lincoln SWR issue "only" when meter inline.

I would look for faulty patch lead, braid, or tip solder joint.
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Old 29th Jun 2021, 11:42 pm   #23
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Default Re: President Lincoln SWR issue "only" when meter inline.

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Originally Posted by SiriusHardware View Post
Damo, did you try adding some more length to the coax at the aerial side of the equation, or failing that, taking some length off? It may have a more dramatic effect if you try it on the coax to the aerial instead of on the patch lead between the radio and SWR meter - although that was worth trying and did cause some change in the SWR.

Here's a thought: You say you don't (or didn't) have any female-female connectors but you do have at least two SWR meters and a selection of patch leads. So what happens if you daisy-chain two of the meters in series (in effect, using the second one as a cable joiner).
Hi Sirius,

Yesterday evening, I thought I'd get on the job again as I found some free time for a change.

I've got a load of new RG8 mini (15M), a couple of new patch leads, a new amplifier, and some barrel connectors.

I didn't try adding any more length to the Coax', nor did I try to exchange the RG213 to RG8 Mini.

What I did do, though, is add an RF amplifier that I found from years ago, and the setup was like this - Rig > Amp > SWR/Power meter > Antenna. The problem now seems to have vanished with the Amplifier switched on or off & with the SWR/Power meter permanently inline.

There is one remaining problem, though, & that is that the rig SWR function is now inaccurate. 1:8:1 shows about 1.2:1, and anything under 1.5:1 shows as perfect SWR.

With the amplifier turned on I checked the input impedance of it, and it was circa 1:4:1. With the amplifier turned off, it drops to nothing.

I did get a "one off" erratic SWR like the initial problem, but it only happening once or twice & wasn't permanent like the initial problem.
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Old 30th Jun 2021, 7:49 am   #24
SiriusHardware
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Default Re: President Lincoln SWR issue "only" when meter inline.

When you have the amp inline, but off, I would imagine there is a pass-through connection so that the SWR meter in the radio only sees the SWR of what is beyond the amp.

When the amp is inline the output of the radio is only connected directly to the input impedance matching circuit of the amp, which may very well present a less than perfect SWR to the radio.

With the setup you are describing the radio SWR meter is measuring the SWR of the input of the amp only, whereas the SWR meter is measuring the SWR of all that follows the amp.

It therefore does not surprise me that the radio SWR meter and the inline SWR meter show different SWR readings in these circumstances. I would be more surprised if they did not.
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Old 1st Jul 2021, 7:31 am   #25
Damo666
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Default Re: President Lincoln SWR issue "only" when meter inline.

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Originally Posted by SiriusHardware View Post
When you have the amp inline, but off, I would imagine there is a pass-through connection so that the SWR meter in the radio only sees the SWR of what is beyond the amp.

When the amp is inline the output of the radio is only connected directly to the input impedance matching circuit of the amp, which may very well present a less than perfect SWR to the radio.

With the setup you are describing the radio SWR meter is measuring the SWR of the input of the amp only, whereas the SWR meter is measuring the SWR of all that follows the amp.

It therefore does not surprise me that the radio SWR meter and the inline SWR meter show different SWR readings in these circumstances. I would be more surprised if they did not.
The SWR readings from the rig are significantly different compared to the external SWR meter even when the amplifier is turned off.

I did an input impedance/SWR test with the amplifier turned on & off, & you're right about the pass through when it's turned off. SWR is the Antenna SWR.

I used another SWR meter between the rig & the amplifier, in addition to checking using the rig SWR function.

With the Amplifier switched on, the input impedance of the amplifier varies from 1.3:1 to 1.6:1 throughout the 27 > 28 Mhz range.

With regards the erratic SWR readings now stopping even with an external SWR meter & amplifier fitted, but erratic SWR readings with just a SWR meter fitted - I'm just going to put it down to RF voodoo.

The rig seems happy at the moment.
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