Help with President McKinley.

Got a President McKinley from Knights CB. Had it widebanded so I could use it on 10m. Decided to check the power outputs today using my MFJ 993 and a dummy load.

On AM it would appear to have "backwards swing" so you key up with no audio and the S meter on the McKinley pegs to the right and as you talk the meter drops. The meter on the 993 shows just short of 15W when keying up and actually goes backwards as you talk. Monitoring on another CB radio and playing a tone so I can use a fixed audio level every time I play the tone the S meter on the receiving CB drops so it's definitely negative modulation. If I drop the RF power down to it's minimum setting on the McKinley it works as it should.

Now this thing to me is screaming it's nuts off. It's a "deadkey" of 14W on AM, it's doing 27W on FM, it's doing 25/26W playing a two tone test signal into the mic on SSB. Talking to my first contact on it on SSB to someone who is about 20 miles from me they asked if I was using a power mike when I told them what radio I was using... 

As we know Knights checks every single radio on the bench before they give you it. Is the backwards swing due to them setting the AM carrier level being set too high? I'm kind of concerned that they're cranking everything up to 11 to keep the idiots happy which is not what I want.

Here are the possible mods on the radio... 



The modulation on AM may have been done in which case your mic gain shouldn't need to be so high and I assume the mod that is done is carried out with the standard mic attached so any aftermarket mic may effect the audio.

Best thing to do is ask Knights what mods have been done and explain your findings to them. The menus are quite vast I believe so it could be a setting which just needs turning off or down.

Yep think I'm going to have an awkward phone call with them. Was using stock mike, unfortunately it's not a menu setting. Got a funny feeling the FM, AM and SSB high power pots have just been wound to the end stops. 

The mic gain being too high isn't the end of the world because it does adjust lower and when playing a tone whilst adjusting it in SSB once it gets to just over half way then the SSB output power starts to drop which it should do so it might be a bit higher but hopefully not excessively so.

I buy new from shops precisely because I don't want golden screwdrivered radios.

I got hold of the service manual. It's screaming it's nuts off as I expected. In Export (RU) mode it should be AM 10W deadkey, FM 20W, SSB 24W.

Northern Crusader wrote:

I got hold of the service manual. It's screaming it's nuts off as I expected. In Export (RU) mode it should be AM 10W deadkey, FM 20W, SSB 24W.

Hi  

Did you get any joy sorting your rig out.?

I have a McKinley too and buy from Knights too so just wondering!

John

Good question John,


I'm sure there are others in the same boat and might be worried.

How did it all work out Conor?

(May well help others and put their minds at ease.)


All the best,
Victor

Hi Victor. 

Yes. I’m finding out all different things about this and my crt 40 ch Space that are not in the instructions nor have I found out from any YouTube video’s. 

Not sure what they gain by not putting it say on line in case there are individual countries that it may violate there legality but I’m sure there must be a way around that. There usually is!

Tristar wrote:

Northern Crusader wrote:

I got hold of the service manual. It's screaming it's nuts off as I expected. In Export (RU) mode it should be AM 10W deadkey, FM 20W, SSB 24W.

Hi  

Did you get any joy sorting your rig out.?

I have a McKinley too and buy from Knights too so just wondering!

John

Spoke with them, they confirmed they just set up the audio levels. I thought sod it and managed to open it whilst keeping the warranty seals intact.

So...power pots weren't at the end stops, they were about 2/3-3/4 so I expect the power it was at was simply down to whoever set it at the factory not giving a toss. Adjusted FM down to 20W, SSB down to 24W, can't get AM DK down to 10W, only 11W but it's near enough. Once you get past a certain point on the AM high power trimmer about midway the power actually starts to go back up which I suspect is due to the way it's configured in the circuit as it's a 3 contact one.

So in regards to the AM meter if you google "Backwards swing" basically it's a phenomenon that occurs because the deadkey is set at a level where when you're speaking peak power can't reach roughly four times the DK.

"For an amplitude modulated (AM) transmitter to produce 100% negative and 100% positive modulation peaks (for overall 100% modulation), the positive peak needs to be about 4x the carrier power. In other words, if you had a legal CB radio that dead keyed around 3 watts, a 100% modulation positive peak would be around 12 watts."


Given it's only possible to get the DK down to 11W in export mode on my radio and it's peaking around 20W on AM, it's not possible to sort the backwards swing and it isn't even if you set it to the service manual alignment value of 10W. It sounds perfectly fine though, nice and clear with no distortion and if I wind back the transmit power in the menu it does start to work the right way round which kind of confirms all of this. I'm perfectly satisfied that if I undid the export mode mod that it would work correctly.

AM isn't a mode I use so I'm not overly concerned but FM is.

Unfortunately my Marconi 2955 radio communications tester crapped itself a couple of years ago and I never replaced it so I've not got anything I can use to check the FM deviation and AM modulation levels and without test gear I'm not going to start random pot twiddling.

So in short it works, it sounds just fine, I'm making plenty of contacts, I'm happy and it's just accepting that it has backwards swing on a mode I don't use. It probably would've been just fine running the original 27W FM and 24W SSB (especially SSB) but I'm one of those people who don't believe in getting every last watt out of something and would rather have it where it was supposed to be and lasting longer. You'll not notice a difference in 24 or 27W over 20W in real world use.

Doug has built a good reputation over the years and doesn't strike me as the kind of person who would stiff someone so I expect that if you buy one from him and be unlucky enough to have issues down the line it'll get sorted.

Hi NC. 

Thanks for such a detailed reply. 
It’s very helpful. 
Although my Mc isn’t opened up it doesn’t mean I won’t and this could help if I want to make sure all is set correctly. 

I’m glad you are happy with your set and that it sounds fine and your making contact. 
That’s the main thing. 

Funny enough we do use AM a bit around here. Now the interfering side seems to be much less frequent we quite often switch on to AM for local chats but rarely distance. 
For me it just gives my ears a rest from the FM noise that can get on the nerves!

I agree about Doug and Knights. I used to order from them back in the late 70s early 80s and have always been customer focused. Probably why they are still in the business

Again thanks for the reply and have a great weekend. 

John

Firetrap wrote:

Here are the possible mods on the radio... 



The modulation on AM may have been done in which case  your mic gain shouldn't need to be so high and I assume the mod that is done is carried out with the standard mic attached so any aftermarket mic may effect the audio.

Best thing to do is ask Knights what mods have been done and explain your findings to them. The menus are quite vast I believe so it could be a setting which just needs turning off or down.

Hi very interested in the above mods, Where in the UK would I be able to have these modifications carried out, my Mckinley was purchased from Knights wide banded at point of sale, would love a custom built cooling fan attached to the cooling fins at the rear also....