"The image rejection is so poor on the top band of many consumer grade
radios that its really a moot point and the
only way to guess which side the injection goes is by evaluating which side
suffers the worse dial tracking..."

Right. I recently went through just this problem. Radio had been twiddled
with. The service information said nothing about whether low or high side
injection was used. I used the trial and error method to figure it out. I
looked through two different service instructions and both were silent.

The good news is that single conversion radios, with 1 rf amplifier stage,
are rarely used above 20 meters anyway, these days.

73, Colin K7FM

On Wed, 18 Feb 2009, COLIN LAMB wrote:

"The image rejection is so poor on the top band of many consumer grade
radios that its really a moot point and the
only way to guess which side the injection goes is by evaluating which side
suffers the worse dial tracking..."

Right. I recently went through just this problem. Radio had been twiddled
with. The service information said nothing about whether low or high side
injection was used. I used the trial and error method to figure it out. I
looked through two different service instructions and both were silent.

I remember one review for a low end receiver, and I can't remember which
receiver or which magazine, and they outright said there was so little
image rejection that they couldn't tell which was real and which was
the image.

On the other hand, I recently reread a review for the Radio Shack sw
receiver from the late sixties, transistorized and something like the
DX-150, and it praised the receiver for it's image rejection even on the
highest band. I suspect it was thus a very generous review.

The good news is that single conversion radios, with 1 rf amplifier stage,
are rarely used above 20 meters anyway, these days.

Of course, that's apples and oranges. The frequency of the IF factors
in, and it's not the single conversion that matters, but the signal
frequency versus the IF frequency.

Michael VE2BVW

On Thu, 19 Feb 2009 00:10:43 -0500, Michael Black wrote:

On Wed, 18 Feb 2009, COLIN LAMB wrote:

"The image rejection is so poor on the top band of many consumer grade
radios that its really a moot point and the only way to guess which
side the injection goes is by evaluating which side suffers the worse
dial tracking..."

Right. I recently went through just this problem. Radio had been
twiddled with. The service information said nothing about whether low
or high side injection was used. I used the trial and error method to
figure it out. I looked through two different service instructions and
both were silent.

I remember one review for a low end receiver, and I can't remember which
receiver or which magazine, and they outright said there was so little
image rejection that they couldn't tell which was real and which was the
image.

On the other hand, I recently reread a review for the Radio Shack sw
receiver from the late sixties, transistorized and something like the
DX-150, and it praised the receiver for it's image rejection even on the
highest band. I suspect it was thus a very generous review.

The good news is that single conversion radios, with 1 rf amplifier
stage, are rarely used above 20 meters anyway, these days.

Of course, that's apples and oranges. The frequency of the IF factors
in, and it's not the single conversion that matters, but the signal
frequency versus the IF frequency.

Michael VE2BVW

Kinda yes, kinda no. It's much easier to get a high 1st IF and a nice
narrow overall response in a double conversion superhet than a single.

Having said that, my Galaxy 5 worked pretty well with a 9MHz IF and
single conversion.

--
http://www.wescottdesign.com

Tim Wescott wrote:

Having said that, my Galaxy 5 worked pretty well with a 9MHz IF and
single conversion.

Apples and oranges since the Galaxy made no attempt to cover BCB range
ad certainly had no BCB parallel.

3200 kc Infradyne comes to mind as a "high IF scheme" for BCB but I
can't think of any older single conversion rig that used a high IF freq
for BCB? Ok, theres some 1600-17oo kc schemes. The older mindset was to
go lower in freq for improved Q.