"Peter Hoon" <[EMAIL PROTECTED]> made an utterance to the drakelist gang ---------------------------------------------------------------------- Want to thank the great list members, Kevin, John, Keith and Garey. This list is a fine resource.
Problem #1: reduced sensitivity: Garey, our TR4-C has an exposed metal wire "loop" as the fuse, and not a #12 bulb. We checked it and it is fine. Tks for suggestion. Somehow, as we worked on the rig on the bench on a blanket, that side switch got pulled backwards, and we didn't catch it (or we should say, the blanket caught it). Once we pulled the side switch forward, we heard a great difference on receive. Fellows, thanks for pointing out our error. Data on receive follows below. Here are receiver sensitivity numbers for a ten db signal to signal plus noise ratio. Measurements are in microvolts across a 50 ohm load placed on 50 ohm coax going into the signal generator. We have a well isolated sig gen and believe "leak through" at low power levels is not a source of measurement error in the numbers below. Please read these numbers below and comment on this question: "Is the receiver section sufficiently within spec of .5 uV (as stated in manual), or do we still have work to do?" Except in the 15M case, as noted below, measurements were done at appropriate upper and lower sidebands, the standard Drake SSB bandwidth, we think about 2.5 kHz (manual does not state the SSB passband). RF tune was peaked for each band. Here are the receiver sensitivity numbers: 80M at 3.6 Mhz: .8 uV for 10 dB S/S +N 40M at 7.1 Mhz: .46 uV 20M at 14.1 Mhz: .48 uV 15M at 21.3 Mhz: .70 uV 15M at 21.3 Mhz, filter in 500 Hz position: .48 uV 10M at 28.4 Mhz: .77 uV 10M at 28.6 Mhz: .85 uV 10M at 29.1 Mhz: .85 uV On 20M, we require 180 uV to get an S9 reading on our TR4-C S meter. On 40M we require 200 uV to get S9. This seems to be quite a bit more than we would expect. (Our Ten Tec Omni 6 plus S meter is set for 50 uV to produce S9.) So even if receive sensitivity is about right, we still have an S meter problem to solve. [Our transmitter output problem still is not solved, that is, weak (two to five watts) output on 80, 40, 15 and 10 (20M seems fine, close to 180 CW watts out, and excellent SSB audio on the air). The details will follow under a different post, but we thought we'd mention this in case this issue is conflated with weak receive sensitivity] This should have been in our first post: We checked under magnification all resistors and components. Chassis bottom is pristine; no charred/over-heated or broken caps/resistors/coils/wire leads. Top chassis is also in great shape for a rig this age; no corrosion, just a few dark smears and spots. All dust and grime has been cleaned out; copper grease on variable cap bearings. Rig used in high, dry Colorado mtn climate for its entire life. So at least on first inspection, we think these possible causes can be eliminated. Thanks again, Peter and Max Nederland, Colorado ---------------------------------------------------------------------- Submissions: [email protected] Unsubscribe: [EMAIL PROTECTED] - unsubscribe drakelist in body Hopelessly Lost: [EMAIL PROTECTED] - help in body of message Zerobeat Web Page: www.zerobeat.net - sponsored by www.tlchost.net ----------------------------------------------------------------------
