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A forum for the discussion of matters of a technical nature. All such activities are undertaken at the readers discretion and own risk. If you don't know what you are doing, don't blame us if it all goes wrong!
Agent 48 wrote: ↑25 Nov 2024, 10:38
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I've noticed power drops as I go down the channels, so channel 1 is half a watt and channel 40 is 6 watts. Channel 19 4 watts.
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That just needs a tune up of the amplifier stage (on a dummy load).
Agent 48 wrote: ↑25 Nov 2024, 21:42
Just an interesting observation I can run 30 watts into my horizontal indoor antenna and SWR is 1:1 on the Murphy or any other old radio with an amp.
On my CRT 9900 SWR is 1.5 and rises upwards at 8 watts??? I can just about run 12 watts safely on the CRT 9900 any mode but other radios give me a flat SWR on the same antenna.
That might be because the CRT9900 outputs more harmonics at higher powers, not on 27Mhz, so not resonant on the antenna.
Yeah the modern rigs are cheaply made junk that sell for top dollar. I'll stick to the old rigs, they are made much better and are clean. I'll probably sell or trade the CRT 9900.
I got another Major M588 which works with the mic from the Murphy radio so mic socket has been rewired, its got some really awful mods where each switch changes the frequency so I have no idea what frequency channels I am on without a frequency counter to tell me what channel the radio is transmitting on. It has the full UK40 FM band with 14 watts output very nice modulation but only 2 watts on AM, I couldn't find the Mids and SSB seems to do a lot of odd frequencies so I'm at a total loss with this radio other than knowing it does UK40 FM.
I may have to send this one off for repair either get it back to standard or have a 10 meter conversion done on it.
My regular rig doctor only deals with legal CB radios and he will not touch this radio so I will have to find somebody who does conversions or repairs to these types of CB radios. I can do basic repairs but when a radio has been messed with in such a way its beyond my knowledge.
I think the best mod for this radio is to have it doing 4watts on FM/AM UK40 & Mid band AM then 12 watts on SSB with the standard legal USB/LSB CB channels.
The very first thing to do is to get yourself a proper frequency counter, I couldn't operate without one for testing out these old rigs. I've just picked up yet another Ham International Multimode 2 from one of the locals. This rig has got some history locally and has featured on the original owners YouTube channel. Unfortunately he sold it on after going through a bad patch and it's changed hands several times since. It's picked up a few more nicks and dings on its recent travels, but it's basically unmolested and original inside, just having had the splits fitted to the CB/PA switch. With the clarifier/KC shift switched to 'off' the low band was virtually spot on frequency, but mid and high were slightly low, so needed a slight tweak to the trimmers with the frequency counter 'sniffing' the coax to bring them both spot on.
I had a Major M588 decades ago and ended up doing loads of mods to it. They're the poor mans Multimode 2 in that they contain the same electronics, but without any of the bells and whistles that make the Multimode 2 such a good rig.
NM1020 wrote: ↑04 Dec 2024, 16:49
The very first thing to do is to get yourself a proper frequency counter, I couldn't operate without one for testing out these old rigs. I've just picked up yet another Ham International Multimode 2 from one of the locals. This rig has got some history locally and has featured on the original owners YouTube channel. Unfortunately he sold it on after going through a bad patch and it's changed hands several times since. It's picked up a few more nicks and dings on its recent travels, but it's basically unmolested and original inside, just having had the splits fitted to the CB/PA switch. With the clarifier/KC shift switched to 'off' the low band was virtually spot on frequency, but mid and high were slightly low, so needed a slight tweak to the trimmers with the frequency counter 'sniffing' the coax to bring them both spot on.
I had a Major M588 decades ago and ended up doing loads of mods to it. They're the poor mans Multimode 2 in that they contain the same electronics, but without any of the bells and whistles that make the Multimode 2 such a good rig.
I may end up selling the M588 as is... I'd probably still get 100 quid for it & somebody will be able to sort it out to there taste. I quite fancy getting a Radioddity QT 60 so I can sell of some of my old SSB junkers and get something that has what I need. I've also got a couple of Tristar 777 rigs one in mint condition untouched. I'll be keeping a couple of my old SSB rigs tho as the older stuff was made better although the newer radios do have everything on them that the older rigs don't. The CRT 9900 that I have is OK but not the best... SWR is always high if I go more than 12 watts but I can do more power on the old rigs without the SWR going up plus I had a power cable almost melt while transmitting on the CRT 9900. I sorted it out tho and replaced those white plastic fuse holders with inline car fuses which I find are much better. The Radioddity QT 60 maybe a better quality rig.
The QT-60 is just a CRT 7900 so I think its all the same cheap rubbish just different designs. Or should I say expensive cheap rubbish. It be worth hanging on to the old SSB radios after all & worth investing money into getting them repaired and tuned up.
I'm thinking about building a base station rig, it could be quite fun.
I have some old broken PC speakers, loud speakers inside are still good for projects. I have a few nice shiny chrome 4 inch speaker grills plus some HP server power supplies, ply wood sheets & 25 watt linear amp. I may also fit a digital clock on it as well. I have an echo box and power mic, plenty of bits and pieces that are useful for a CB base station build.
First thing I would need to do is test to see how suitable the server PSU will be as this will be the built in power supply that will power everything but because it will be so close to the radio inside the box I will need to test to see if it puts out any noise on the band first.
I need some resistors for the PSU which I have ordered but doesn't look like they will be arriving... Christmas mail chaos... I might have to wait until after the New Year to order parts I need to test the PSU otherwise I will search some old circuit boards I have... to see what I can use so I can test the power supply and get the build on the way.
