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All sorts of interesting stuff about Ham Radio and old gear from Steve G3ZPS, near London in the UK

KW Atlanta


Next KW item added to the inventory a very nice KW Atlanta transceiver with matching external VFO, PSU and Shure 444 microphone. This has been well looked after and is in first class cosmetic and elctrical condition

At some point in its past life its been modified to use 6146 tubes in place of the 6LQ6 'sweep tubes', this appears to have been well done and the power out on 40 and 80m is around 100w. The original design claimed 500W PEP input and despite the marketing hype the rig could probably exceed 200W out in its unmodified state With the 6146 valves the output drops off on the higher bands, but it runs cooler and puts less strain on the PSU

As it was in regular use before it came to me there was very little restoration work to do, although as with all older kit I will change the PSU caps for more modern ones - and for some reason the HT choke in the PSU is missing.

There are very few Atlantas on the air in the UK and little information on the web about them..initially aimed at the US market, KW did sell them in the UK from 1969.

The KW Atlanta is pretty much a direct component level rip-off of the USA Swan 500 ( I have checked the schematics!). OK so they look a 'bit' different, but the radio architecture, tube lineup, audio derived AGC, dial arrangement are all identical..I have no idea how KW got away with copying a US rig, knocking it up in the UK and selling it back in the US!. 

KW copied the PSU as well but made it cheaper (surprise), the smoothing capacitors are all held together with cable ties and one bolt. The carrier 'bal' control is a nightmare in 'tune' mode - all the way left does not mean OFF, thats in the middle..turn all the way to the left and your back to lots of anode current...caught me out and probably quite a few other hams over the years

Unlike the Atlanta the Swan 500 manual is a delight and I could probably use it to fault find the Atlanta, pity KW didn't copy that as well !. To cut cost the Swan design doesn't have any crystals as a premix to a 1st IF, instead the VFO frequency is switched by a bank of caps - of course KW copied this as well.

Its a cheap 'Single Conversion' design with drift and poor dial calibration (worst on 10m) and lots of VFO trimmers. Thi pi tank is used on receive as well as TX.

Having said all that its fine on the low bands and the audio is very good if you back off the RF to stop the audio derived AGC pops. On both recent KW activity weekends (2017 amd 2018)  the rig has perfomed without a hitch hour after hour on 80m and 40m. I have included a pic of the Swan 500 - same radio but better built.

In Jan 2017 I noticed an annoying problem with the Atlanta that had probably been getting worse since I obtained it..the S meter would gradually move upscale as the rig warmed up - as if the RF Gain was being backed off.  A blip of the PTT put the S meter back to near zero (if no signal was present) and then it would gradually move upscale over 15 mins. This was clearly an AGC fault as the rest of the radio was fine.

Before pulling the radio apart I searched for AGC faults on the SWAN 350/500 and sure enough Chris GM3WOJ (also an avid KW collector) had come across the same problem in a SWAN. There is some sort of diode clamp in the AGC circuit (not sure what it does - there is no info in the manual)..but if the diode leaks a tiny bit it gradually deafens the receiver. It took me a few mins to find it (no layout diagrams exist), but I changed it for a 1N4001 to see what would happen...problem solved