1254 Review by Paul Bigelow

From the Ten-Tec Reflector April 1, 1998

I have built the 1254 receiver and it is a nice little unit. A real joy to build, use and tune around. I haven't had this much fun in ages!

Features:

1. Great sensitivity (compared against the NRD-525) and the sensitivity is relatively consistent across the 100kc-30000kc receiving range.
2. Good selectivity (for a 4kc filter)
3. Reasonably stable
4. Excellent quality boards
5. Easy to service (except for removing parts from the plated through holes)
6. Convenient to use
7. Informative, relatively easy to follow instructions

Suggested change:

Mount an RCA jack with a nylon washer on the outside to the back panel to reduce stress on the board.

Quirks noted and possible remedies:

• Lots of birdies and display induced signals on the lower half of the AM broadcast band.
  • Remedy: Have attempted to shield out the multiplexing emissions by spray painting a graphite EMI/RF shield to the inside of the front cover. It helped a little bit.
• Reduced sensitivity on the lower half of the AM broadcast band.
  • Remedy: Put a jumper across R72, eliminating that input filter.
• FM intermod from strong FM stations. Just add 90 (2* 1st IF) to the received frequency to detetmine offending frequency.
  • Remedy: Have tried with some success (but none totally satisfactory):
    • Snap-on RF choke on power cable
    • Soldered on a shield on trace side of the board around the 1st Mixer section.
    • Incorporated FM trap (from Radio Shack) in the antenna lead.
• The rotary Encoder loosens up with use causing the frequencies to jump around (sometimes) when tuning from one step to another.
  • Possible Remedy (have not tried yet): Sandwiching a large, black, felt washer between the tuning knob and the tuning knob recess to reduce play.
• Hum from the power supply.
  • Possible Remedy (have not tried yet): Install a 15V IC regulator in the power supply.
• Deafening thump upon turning on the 1254 when using headphones. REALLY LOUD.
  • Remedy: None yet although I suspect a large capactior may resolve this one.
• A little bit of "thumping" due to slow synthesizer lock. Not too bad, really, considering the price.

Paul