LAFAYETTE HA350 RECEIVER
  
[picture coming soon]

This article was meant to be about a comprehensive overhaul and upgrade for the classic ham band only receiver produced by Lafayette as a poor man's HQ170. It has a 2 Kc wide 455 Kc IF filter and coverage of 80 through 10 Meters standard ham bands. Here are its impressive specifications: http://wa2iac.com/ha350.html

I found this as almost a discard, with a rusty case. I frequently pick up "rescue" cases like this to prevent their destruction. It was always on my bucket list, since I coveted it as a teenager during my post Novice license first year. I had the case sandblasted and repainted it with rust reformer black. It looked nice as a black case, not the original bluish. I dove into the electronic repairs.

The architecture of this radio is a basic 80 Meter receiver fed from a down converter using the 80 Meter receiver as a tunable IF. The second IF is 455 Kc. It has a good product detector, as well as an AM detector. A decent audio amp follows it all up.

The original owner had replaced a lot of the capacitors. However, he mis-adjusted the coils for the conversion crystals for the upper bands. Some of the bands were dead. The injection voltage is a compromise due to only one adjustment coil for upper frequencies. This results in less than optimum sensitivity. The switch allows for separating the band selection and installation of individual coils for each band selected. If you install a separate transistor crystal oscillator to drive the 6BL8 mixer-oscillator tube (using the oscillator section as a buffer amplifier), this further improves things. The 6EA8 has the same pinout and more transconductance in the triode section. It could be a viable substitute and make the transistor oscillator modification unnecessary. The 6BL8 is a little hard to find these days.

It is possible to expand the coverage beyond the original frequencies. A built in bonus is the 11 Mc crystal has a second harmonic on 22 Mc (minus 4 Mc equals 18 Mc or 17 Meters!) With the addition of transistor oscillator as described above with a tuned circuit at 22 Mc, this would work better. It actually almost works in the stock receiver if you tune the preselector properly.

The only other deficiency is the selectivity of the preselector in the presence of strong foreign broadcast signals outside the ham bands, particularly on 40 Meters. An active preselector or a simple tuned circuit ahead of the HA350 would correct this easily.

Also, I wanted to provide an AM bandwidth ceramic filter from the junkbox. Some reed relays would switch it in when AM was selected.

I never had a chance to attempt these changes, but they are offered to anyone interested in experimenting. I recently acquired a Yaesu FT950 and needed to raise some cash to fund that purchase. I sold this radio as a stock working unit at a swapmeet.

  

73,
Janis
AB2RA
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