IF Gain vs. RF Gain
 

I have an HE-10 with an IF Gain control. The manual says to turn it
all the way for AM reception. Is this the same thing as an RF gain
control? The RF Gain on my Panasonic 2200 controls the sensitivity,
and so does the IF gain on the HE-10. So, what is the difference?
--
"What do you mean there's no movie?"

IF Gain vs. RF Gain
 

"Count Floyd" (CountFloyd@MonsterChillerHorrorTheater) writes:
I have an HE-10 with an IF Gain control. The manual says to turn it
all the way for AM reception. Is this the same thing as an RF gain
control? The RF Gain on my Panasonic 2200 controls the sensitivity,
and so does the IF gain on the HE-10. So, what is the difference?

The manual says "all the way..." what?

The HE-10 is a Lafayette cheapie, or is it some comletely other
receiver? Because I have a vague idea that the receiver I'm thinking
of used regeneration in the IF amplifier to provide a locatl beat
oscillator for CW reception. And in that case, varying the IF gain
would affect whether or not the stage went into oscillation.

RF gain and IF gain will affect things somewhat differently, but
not in terms of overall gain. Some receivers may not even have an
RF stage. The point is to reduce the overall radio gain (as opposed
to audio gain) for various purposes, mostly to prevent overload. A
receiver that had both RF and IF gain controls, and I seem to recall
that some did, in terms of gain it wouldn't matter which one you played
with. But it might matter in crucial issues. If a local station was
overloading, reducing RF gain might reduce or eliminate front end overload,
because the signal wouldn't get amplified much before there was good
selectivity, while if you reduced IF gain for the same signal, it would
have no affect because it was the RF stage being overloaded.

The real time you'd see much mention of RF or IF gain controls was
in dealing with SSB, once it came along. For receivers that had no product
detector, you were told to reduce RF gain and then increase audio gain
(to compensate for the reduced RF gain, in effect overall gain would remain
the same or close to it while the distribution of that gain would change).
This was so the incoming signal was weak compared to the receiver's BFO
signal, because it needed to be much stronger than the incoming signal in
order to properly demodulate the SSB signal. In this case, it wouldn't have
mattered whether you had an RF or IF gain control, or which one you used
if you had both.

Michael

IF Gain vs. RF Gain
 

The He-10 was a pretty good receiver considering the price. It was
conventional and did not use a regen if.

Perhaps the reason to use full if gain for am would be to allow the s-meter
to read accurately and also allow the avc to work effectively.

The if gain and the rf gain do basically the same thing. If there are
really strong signals, you would like to reduce the gain before the first rf
stage to prevent overloading of the rf amp and mixer. However, a gain
control in the rf amp can affect noise figure and signal handling. Perhaps
the engineers working on it were not satisfied with the signal handling
capacity when they changed the parameters of the rf amp with the rf gain
control (I suspect that is the reson).

Performance would be equivalent to the Hallicrafters SX-99. It was a
physical copy of the old S-38. Note that the tube line up shows that remote
and semi-remote pentodes were used rather than sharp cutoff, so the radio
was designed to perform as well as it could for the price.

Colin K7FM

IF Gain vs. RF Gain
 

On Tue, 4 Jul 2006 03:34:30 UTC, (Michael
Black) wrote:

"Count Floyd" (CountFloyd@MonsterChillerHorrorTheater) writes:
I have an HE-10 with an IF Gain control. The manual says to turn it
all the way for AM reception. Is this the same thing as an RF gain
control? The RF Gain on my Panasonic 2200 controls the sensitivity,
and so does the IF gain on the HE-10. So, what is the difference?

The manual says "all the way..." what?

The HE-10 is a Lafayette cheapie, or is it some comletely other
receiver? Because I have a vague idea that the receiver I'm thinking
of used regeneration in the IF amplifier to provide a locatl beat
oscillator for CW reception. And in that case, varying the IF gain
would affect whether or not the stage went into oscillation.

RF gain and IF gain will affect things somewhat differently, but
not in terms of overall gain. Some receivers may not even have an
RF stage. The point is to reduce the overall radio gain (as opposed
to audio gain) for various purposes, mostly to prevent overload. A
receiver that had both RF and IF gain controls, and I seem to recall
that some did, in terms of gain it wouldn't matter which one you played
with. But it might matter in crucial issues. If a local station was
overloading, reducing RF gain might reduce or eliminate front end overload,
because the signal wouldn't get amplified much before there was good
selectivity, while if you reduced IF gain for the same signal, it would
have no affect because it was the RF stage being overloaded.

The real time you'd see much mention of RF or IF gain controls was
in dealing with SSB, once it came along. For receivers that had no product
detector, you were told to reduce RF gain and then increase audio gain
(to compensate for the reduced RF gain, in effect overall gain would remain
the same or close to it while the distribution of that gain would change).
This was so the incoming signal was weak compared to the receiver's BFO
signal, because it needed to be much stronger than the incoming signal in
order to properly demodulate the SSB signal. In this case, it wouldn't have
mattered whether you had an RF or IF gain control, or which one you used
if you had both.

Michael
Thanks for the reply, yes, this is the Lafayette HE-10, in mint
condition, recently recapped and aligned. The manual says to put the
IF gain control at maximum for AM reception, and to reduce it if it
overloads the receiver. The radio is very sensitive getting really
good DX here in South Florida.
I was just curious whether the IF gain was similar to the RF gain in
my other receivers. The radio also has a BFO pitch control for
CW/SSB, and a switch for AVC/MVC/BFO.


--
"What do you mean there's no movie?"

IF Gain vs. RF Gain
 

"Count Floyd" (CountFloyd@MonsterChillerHorrorTheater) writes:


Thanks for the reply, yes, this is the Lafayette HE-10, in mint
condition, recently recapped and aligned. The manual says to put the
IF gain control at maximum for AM reception, and to reduce it if it
overloads the receiver. The radio is very sensitive getting really
good DX here in South Florida.
I was just curious whether the IF gain was similar to the RF gain in
my other receivers. The radio also has a BFO pitch control for
CW/SSB, and a switch for AVC/MVC/BFO.

Someone else replied already and said it's not a cheapy, and your
description here does not make it sound like such. Of course, now I'm
hving a problem picturing which receiver it was.

Michael

IF Gain vs. RF Gain
 

On Tue, 4 Jul 2006 04:23:15 UTC, (Michael
Black) wrote:

"Count Floyd" (CountFloyd@MonsterChillerHorrorTheater) writes:


Thanks for the reply, yes, this is the Lafayette HE-10, in mint
condition, recently recapped and aligned. The manual says to put the
IF gain control at maximum for AM reception, and to reduce it if it
overloads the receiver. The radio is very sensitive getting really
good DX here in South Florida.
I was just curious whether the IF gain was similar to the RF gain in
my other receivers. The radio also has a BFO pitch control for
CW/SSB, and a switch for AVC/MVC/BFO.

Someone else replied already and said it's not a cheapy, and your
description here does not make it sound like such. Of course, now I'm
hving a problem picturing which receiver it was.

Michael
Michael,
It looks like an S-38 on steroids! It has 9 tubes, the familiar
half-moon dials, an "S" meter and it has a transformer, not the "hot
tail" setup of the old S-38 ( of which I have the C model, fully
restored).


--
"What do you mean there's no movie?"