This is an old revision of the document!
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:
- Great sensitivity (compared against the NRD-525) and the sensitivity is relatively consistent across the 100kc-30000kc receiving range.
- Good selectivity (for a 4kc filter)
- Reasonably stable
- Excellent quality boards
- Easy to service (except for removing parts from the plated through holes)
- Convenient to use
- 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