003: 7MHz SSB/CW receiver (7360 mixer)

 50MHzのSSBをやるための親受信機である。コンバータのイメージ比が取りやすいこと、いつも実際の交信が聞こえて調整に便利なことから周波数帯は7MHzとした。1976年~77年にこれを製作した当時のラインナップは6AH6(mix), 6AU6 (VFO)-MF (国際MF45510AZ)- 6BA6*2- 6BE6 (DET), 12AU7(BFO)-6BM8 オール真空管だった。その後性能アップのためミクサを7360、VFOを2SK19*2、検波をSN16913、AFアンプをLM380に変更した。時間を掛けたのはAGCで、回路方式や定数は何年もいじくりまわしたと思う。MOS-FET(3SK35,45,53)のコンバータ群をつなぎ、サイクル21の6mバンドでアジア、北米、南米、オセアニア、アフリカなど多くのDX信号を捉えた思い出深い受信機で、現在は250Hz X’talフィルタも搭載し、7MHzのQRPP交信にも使用している。
7.00-7.24MHz SSB (2.3kc), CW (250Hz), S/N more than 10dB (0dBµV input), image ratio 70dB, AC100V

This is the receiver to connect a VHF converter to do VHF-SSB. Because the image ratio of the converter is better, and an actual contact is always easy to catch, I set a frequency band to 7MHz and it was very convenient for an adjustment of making. Line-up was 6AH6 (mix) and 6AU6 (VFO) -MF(kokusai MF45510AZ) - 6BA6*2- 6BE6 (DET) and 12AU7 (BFO)-6BM8, It was all vacuum tube ! when this was made in 1976-77. Later, I chose RCA7360 for the mixer and VFO of 2SK19*2 and detector of SN16913 (Gilvert cell) and the AF amplifier were changed to LM380. I think it was AGC that I spent much time to improve on this receiver. The circuit system and the fixed number were modified for years. Asia, North America, South America, Oceania and Africa, this receiver worked in a pair with MOS-FET converters, and caught many DX signals on 6m band of cycle 21. A 250Hz X'tal filter is loaded and it's being also used for a QRPP work of 7MHz at present.
7.00-7.24MHz SSB (2.3kc), CW (250Hz), S/N more than 10dB (0dBµV input), image ratio 70dB, AC100V




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