RadioBanter - View Single Post - SB-303 heathkit repairs

dave · July 20th 14, 04:50 PM posted to rec.radio.shortwave

On 07/19/2014 11:26 AM, wrote:
On Saturday, July 19, 2014 10:04:10 AM UTC-4, dave wrote:
On 07/18/2014 05:36 PM, wrote:

On Friday, July 18, 2014 12:29:27 PM UTC-4, Michael Black wrote:

On Fri, 18 Jul 2014, dave wrote:

On 07/17/2014 04:49 PM, Michael Black wrote:

On Thu, 17 Jul 2014, Scott Smith wrote:

SB-303 heathkit repairs, I bought a heathkit SB-303 radio off ebay,

all it gets are various tones when I tune the dial, any idea on

repairs, thanks in advance, email .

Does it have the crystals? If that's the ham band one (rather than the

one for shortwave), the crystals are the same frequency as used in the

full SB line of ham band equipment. Buying crystals these days has

become quite expensive, so if someone needed the crystals for whatever

reasons, they may have stripped a receiver, rather than buy the crystals

new, or find a set of crystals on the used market.

It's a receiver that tunes a 500KHz segement (I think around 3MHz) with

a crystal controlled converter ahead of it, a crystal needed for each band.

Michael

Anybody roll their own quartz crystals? You need an oven. Big bucks for

energy.

I gather the radio magazines did show how to make your own crystals, back

in the thirties.

I'm sure they started with a slab of quartz, and cut it down and started

grinding.

Michael

Very , very difficult. Even after it is close enough(!)in resonant frequency- there are a few MORE extremely critical parameters involved ... This is why true "Crystal Filters" were so expensive,even when they were mass produced ...

You can get nice 5 pole filters for about a hundred bucks can't you (I

haven't checked for a few years). For relatively wide band SWL cascaded

ceramic resonators should suffice).
The current production from Inrad or Icom are around $150 and even higher for the really sharp ones...Insofar as the ceramic resonators go- yes,the prices are extremely low,but so is their Q factor.

Inrad doesn't stock 5-pole filters, but I get it. My ham HF/6m
transceiver IF is 8215 KHz, an aeronautical or military band as I
recall. There might be a big pile of old Bendix or Collins radios
somewhere full of such crystals. The best filters I used for SWL DXing
were the Collins Torsional Mechanical BPFs in my R390A. Unfortunately
they had a 90 pound 26 tube infrastructure required to use them. The
Sony 2010 had fairly good ceramic filters when used with the synchronous
detection. (The K3 has synchronous AM reception, done in DSP). The good
old days of strong backs and cheap electricity are long gone. If I was a
rabid SWL I'd get a K3/10 with the General Coverage input filter set.
Otherwise something direct conversion DSP that doesn't need Windows. I
make do with an HF-150, which is the opposite of filtering.