SWR reading with Amplifier in-line

Hi All,
    This might seem like a stupid question but here goes.................!!
I have a President McKinley connected to a dipole antenna whose SWR on an external meter is just a tad above 1:1. The same reading is shown on the SWR meter built into the McKinley.

When I connect my solid state 50W amplifier and check the SWR on the Mckinley meter the readings are somewhat higher. For example with the amplifier switched off but inline the SWR is around 1.8 and with it powered on the SWR increases to around 3 on the McKinley meter.

Is this expected behaviour or do I need to worry?

Here's my theory...............
I think maybe the higher apparent SWR reading with the amplifier powered on is because the meter in the radio doesn't know there is an external amplifier connected so is just measuring the reflected power but calibrated against what the inbuilt RF Power amplifier delivers which could well be a significant amount relative to that.
I kind of like this theory but then why is the SWR around 1.8 with the external amplifier powered off, that just seems weird to me?

Of course I don't want to damage my McKinley so thought i'd throw the question out there!

Thank you

Lynton

The matching of the amp when on seems a bit poor, may it can be adjusted??

Hi,
    Thank you for the reply.
Yes the amp is definitely not looking healthy. I think I may just bin it rather than mess around and possibly cause damage to my radio.
I bought it around 30 years ago but never used it so its still as new in its box or at least it was until I tried it yesterday!
I did make an earlier post here entitled "CB-Master CB-50" referring to this amp and the possibility of the relays or capacitors being an issue after being in storage for so long. Certainly the relay clicks over when the amp is presented with RF and has a suitable delay before dropping out when on SSB but that of course doesn't mean the contacts are healthy.

Looks like there is an issue.

Lynton

Hi..
I have the same problem with the rk lm 203 amp...
As soon as I turn the amp on swr increases .there are no filters in these amps so it's reflected and increases swr..
With my vertical dipole wire antenna if I use a 1.1 balun swr stays as it is ...
Regarding hi swr with the amp my radio has a high swr warning and when I used a different antenna with the amp the swr went to 3 and the swr warning didn't sound so I have come to the understanding the swr must be ok just reflection coming back along coax...
My next purchase will be a low pass filter to use with my kl 703...
I even tried a 1m coax from the amp to swr meter as I read that helps ,it didn't do anything . ..
Hope this helps
Lee

Hi Lee,
     Thanks for your reply. It would indeed appear that you are observing something similar to me.
My dipole is horizontal with a commercial 1:1 balun installed.
I have now purchased an RM-KL60 and will fit my Low Pass filter between the radio and amp.
Given my antenna SWR is OK and I have the balun I really don't see what more I can do.
Buying the replacement amp will at least go some way to ensuring the amp itself isn't faulty!
The original amp I mentioned is unused but 25+ years old so maybe its dead.

I will post my findings here when the new amp arrives.

Kind Regards

Lynton

Hi lyton
Keep me posted as I have been sorting this problem since January....
I need to get a low pass filter I think that may sort the problem on my other antenna..
Been doing some more reading (alot of information about this on the internet)also try the low pass filter after the amp as well as before it....
Regards lee

If your SWR is good with just the antenna plugged in then that's it.
When you put the amp in line it will show bad SWR but take no notice that is how it has always been.
Well that is in my 40+ years in radio.

Hi Alan...
That's what I thought because the high swr alert isn't going off on the radio...
But then I heard that there is a mismatch somewhere..
You can do so much reading on the internet and fills you're mind with stuff lol...
I'm glad you have said that Alan ..
All the best to you.. lyton is just worried that his old amp maybe a bit knackered so will see what happens when his new one turns up
Lee

If he has an Amp readout on his power supply then turning the amp on will show a bigger draw if it is working.
SWR id power reflected back from your antenna so if it is set right to start with then job done as it won't alter the antenna at all.

Why does it reflect back with some makes of burner and not others?
I have read on forums of people putting variable capacitors somewhere inside to stop the reflection ,that's a bit too involved for me...
As long as it's just reflection I won't touch it then..
I am waiting for my new kl703 to turn up I have heard that at full power the swr goes hi that's what people have said you have explained it as reflection so I'm a happy now..
Thanks alan

I've done over the years and agree with what Alan has said above about swr with just antenna connected first then put amp in-line after

Hi everyone,
    This has turned out to be an interesting discussion so thank you all for the replies and comments.
I now have my new RM KL60 amp so here's what I see now.

With no amp inline I see an SWR of 1:1 on both an external meter and on the SWR meter built into the McKinley.

When I add the KL60 I see an SWR of 1.6:1 on the built in SWR meter with the amp powered off.

With the amp powered on I see an SWR of 1:1 on the built in SWR meter.

I'm happy with that so it would appear my old amp although new and unused for 30 odd years was faulty or at least a very questionable match!

Kind Regards

Lynton

I'm glad it's all sorted and working well..
Lee

Lee,
    Well its doing all the right things now but I am yet to make my first DX contact.
The band was open yesterday evening to Spain, Germany, Switzerland and Italy but I couldn't make anyone hear me sadly.
I remember thirty years ago things were easier than that so maybe my antenna leaves a lot to be desired this time round.
Years ago I had a Thunderpole III while now I have a horizontal half wave wire dipole with balun.
When I have some holiday off work I want to try my hand at building a Delta Loop fitted with a 4:1 balun.
I'm also a bit concerned that the FM audio level on my McKinley is a little low with the standard Mic.
I do have a K-PO Power Mic but would very much like to get a "radio check" with a local so I can experiment with levels etc before pressing that into service.
The problem with that is there appears to be very very few locals active!

Lynton

I was on last night about 6.30 good skip my antenna is pointing south,the trouble I have is the French wipe everyone out ..
Same with some of the Italians they love a bit of power..
I had a nice chat with a chap from the Algarve yesterday about half two when there wasnt much skip about he was on 27.540 he was on a homemade moxon and was getting to me very well..
Where abouts are you ? I might be able to help with you're rig check...
The delta loop sounds like a good idea I was looking at them before I got the moxon...
Regarding you're Mike make sure you turn the mike gain down in the radio to about 30...that's what I have to do in my 6900 when using a power mic
Regards lee

Lee,
    Ha ha yes the Italians they love it!
I'm in Peterborough. I see you're in London so I don't think a contact between us is going to be doable sadly.
Back in the early 90's when I had my better antenna and a slightly better location not far from where I am now I remember Watford was just about doable but that was all.
Yes turning down the Mic gain with a power mic isn't a bad idea, I hadn't considered that. Certainly with the standard President mic it needs to be at max from what I understand!

Cheers

Lynton

Have lynton
I won't be able to help with you're rig check sorry...
Last Saturday Muppets channel 19 scotland stations where coming in louder than people near me skips a funny thing..
There should be someone up you're end to help with you're rig check...
All the best