Me too. SA612 is now apparently out of production, so I’m guessing it uses one of the newer Analog Devices AD-series mixers, but who knows. Any info would be most interesting.
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The KX1 design is a very simple Rx by today’s standards, initially I did not think two NE602’s and an emitter follower would have enough gain in conjunction with the 1.2m whip on 20m and above to be usable. Also, as noted further below, SA612s are no longer made, so I’m hoping it has a more modern mixer(s).
I went back to the Users Manual which includes a short ‘Theory of Operation’ narrative. It states the IF is 9.215MHz, the VFO uses a modern synthesiser/divider that generates the signal in the GHz range and divides it down to minimise phase noise. AGC is developed from audio output to a Darlington pair which is then applied to pin 1 of both mixers for AGC action. This is a commonly used mechanism used with SA612 mixers.
Another found hint is that the crystal filter is 4-pole.
So, maybe the KH1 is not that different to the 20 year old KX1 after all! Sooner or later, someone will take the back off and some questions will be revealed (unless the ICs have been scrubbed).
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Why not. Albert Einstein said: Explain physics as simply as possible, as long as everything stays correct.
I understand it this way: Design as simple as possible while it still works.
73 Chris
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Einstein was brilliant at explaining technical things as in the famous telegraph/radio explanation.
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Of course! And a joker too 
A simple but correct explanation: Long before humanity, evolution invented nerves as electrical conductors. If you pull on the cat’s tail, the brain experiences this via an electrical impulse. However, electrical impulses are not transmitted in conductors by flowing electrons, but by electromagnetic waves. If you leave out the conductor, i.e. the tail, it could still works like with radio waves by using antenna ect,
73 Chris
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Except that nerves don’t propagate signals in anything like the same way as wires do. It’s an electrochemical mechanism rather than electromagnetic waves, and is many orders of magnitude slower.
In reality, the analogy doesn’t work at all.
Martyn M1MAJ
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Which is why it’s funny. Especially when it is attributed to an extremely clever person who would know all the errors in the analogy.
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Quite. Trying to make it “work” rather spoils it.
Martyn
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Thanks for spoiling it Martyn. 
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Au contraire, many radios involve CAT nowadays 
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[quote=“MM0EFI, post:89, topic:33632”]
Thanks for spoiling it Martyn.
[/quote]…
I wasn’t commenting on Einstein’s original…
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Like Einstein, I was attempting humour
Since Elecraft won’t ship the KH-1 to the UK or EU countries (no CE approval) and the only option is to pay an excessive markup to an EU distributor to maskerade the KH-1 as a kit, I was pleased to see on YouTube that EA5IW has demonstrated a more cost effective alternative:
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Ok, so what was the rig??? I can see the key and whip but can’t read the tcvr info. or where the battery was.
Thanks.
73
Ron
VK3AFW
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Hi Ron
If you open the video in YouTube and click on the description it mentions an SW20 and diamond antenna, may be Small Wonder Lab transceiver.
73
Graeme
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I think it won’t be long before someone has installed a QMX in another housing that also has space for a battery. An antenna and a key shouldn’t be a problem.
73 Armin
As this guy did… (c) groups.io
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What is that? A hand held spark gap transmitter?!
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KH1 news: some KHPD1 paddles were manufactured with the wrong springs and will be replaced [Elecraft] KH1 keyer paddle spring to be changed; replacement paddles to be shipped to all affected users
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