The AM is still alive in Japan !


Sept. 10th, 2005 You are the 4359 + counterth visitor
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From left to right, 811A pp Modulator, 813s Final stage, 6146 Excitor


< Receiver >

Old fashon receiver using ST-shape tubes. But available for AM-Stereo ! who knows why!?

(1)Starting with Hi-Fi receiver using variable band width IF transformer with Hi-Fi spec AF amplifier. It was a story about 30 years ago.

(2)Modified for dressing-up as first stage modification ; I tried to build wood-cabinet in 1998.

(3)Then the 2nd stage modification was " A Road to the AM Stereo Receiver" Here is a modification memo.
It had been growing even after the Stereo, modified again and I put synchronous detector then.

(4)and again... Finally, the receiver contains a Mechanical filter for SSB/CW.




< Transmitter >

(1)The first one is my favorite that is operated as an Exciter in the transmitting system.
This is a nice transmitter using 6146 as final stage, modulated by 6BQ5 p-p. I think this is the most popular structure of AM transmitter in late 50s - 60s in JA. I'm using this transmitter as an exciter for high-power(still middle/QRP power in US?) PA.

Circuit diagram




(2)Modulator using 811A p-p.
The modulator was first designed as the modulator with 807 p-p, and this worked pretty well as 100 W audio. But after I completed 813 PA, this looks not to strong enough for the system. So I modified it to 811A pp.

Circuit diagram




(3)hThe Staringh 813 desktop final stage Power Amplifier using RCA 813s.
Running about 120- 140 Watts for carrier output. Because of the size of tha land of JA, I think 100 W carrier is good enough for JA domestic QSO. Even for this type of AM PA, we need to use huge parts that are for more than 500 Watts transmitter, although only 25 ? 30 Watts signal(side band signal for true audio) will be able to reach to / catch on SSB receiver. This looks AM to be "Mottainai" emission mode in terms of its power efficiency.


Circuit diagram @






Modulation Characteristics

Sign wave 800Hz



Psudo-voice wave





July 23rd, 2006, I had a memorial QSO of 2-way AM with JH1MSB in Yokosuka.

Recording: 1 and 2

I was using call sign of "JA1XCT", Tokyo area residence. I was QRV from Mihama-ku, Chiba city, about 30 miles east of central Tokyo.

The receiver I used was the RF-1 IF-2 radio receiver above working with old TRIO RF-amplifier, SM-5. Also I was using 25 meter length three bands(3.5/7/10MHz) Invee antenna about 10 meter high.
The sound I recorded was from direct record using microphone.



in Nara, in 2012

In 2012, in Nara, about 300 miles west of Tokyo, I am QRVing so active on 40 meters AM using the 813 and 811A system above. The antenna Ifm using here in Nara is 15 meter high Inverted Vee beaming 10 deg-190 deg. Since we have AM frequency in JA; 7195 and many stations are there every day, Ifm enjoying AM ham QSO !

Sorry, some pages still left in Japanese.
But I believe circuit diagram would be the common language for us !

Go to my general homepage in JA, Index of Home-brewing