EMRFD Message Archive 1412

Message Date From Subject
1412 2008-02-05 14:56:05 Thomas S. Knutsen IF module
I'm in the prosess of designing an IF module, parts of this would be based
on the Belthorn SSB IF module, using ADE-1 mixers and the Inrad 9MHz filter
kit. The main reason for this design is to make an smal IF board for use in
some portable VHF and UHF rigs, so the size and power drain is important.

The Belthorn module uses MC1350 IF amplifier, this is as I understand
obsolete so, is there any other sugestions on other IC's that can be used
instead? An other tougth is to use the IF amplifier from page 6.76 in
EMRFD, I do feel it is a bit waste to use an HYCAS module, I don't think I
need all that gain. But I guess I'm going to need aprox. 120 dB dynamic
range in the receiver, so it migth be an idea to apply AGC to the front end?

On transmit I'm going to use an MAR2 or MAR3 amplifier to compensate for the
losses in the crystal filter. I can't see any reason to have excessive gain
in the transmitt patch between the modulator and crystal filter?

73 de Thomas LA3PNA
1413 2008-02-05 20:26:56 Allison Parent Re: IF module
1416 2008-02-06 01:15:44 Leon Re: IF module
----- Original Message -----
1417 2008-02-06 07:17:33 Greg Derda Re: IF module
W8DIZ sell's MC1349's here.....



> The Belthorn module uses MC1350 IF amplifier, this is as I understand
> obsolete so, is there any other sugestions on other IC's that can be
> used
> instead?

[Non-text portions of this message have been removed]
1418 2008-02-06 07:17:36 Johan H. Bodin Re: IF module
Allison Parent wrote:
> MC1350s are still reasonably easy to find and there are many vendors
> still selling them. I not certain they are even out of production.

Lansdale Semiconductor Inc. produce "old" chips that have been
discontinued by many other manufacturers, including Motorola. Their
MC1350 replacement is called ML1350.


Johan SM6LKM
1423 2008-02-07 07:26:03 wa7mlh Re: IF module
Based on what you have posted, I have some comments/feedback.

Based on the data sheet performance of the ADE-1 mixers, I see no
relevant difference bewteen the ADE-1 and/or TUF-1 and/or TUF-3
mixers for the aplication you have presented.
I have used all of them in different home brew rigs.
I have been usiing the ADE-1 mixers lately simply because I got them
for a lot less money than what I could get TUF series mixers for.

The "marketed" conversion losses are not necessarily realistic when
you look at the actual data in the data sheets. What I mean here is
that a stated typical loss of 5dB is in reality much closer to 5.5dB
to 6 dB when put in to actual use. And the same goes for the TUF/SBL
series mixers. The point here is that for the typical level 7 diode
ring mixer, expect 5 dB conversion loss at best, and don't be
surprised to get 6dB. For an IF system the differences between any
of the level 7 diode ring mixers from mini circuits will be neglible
in the "big picture".

Last time I checked, there were still numerous "new old stock"
sources for the MC1350 at reasonable prices.

Did you mean 120 dB of receive gain or did you really mean 120dB
dynamic range?

I am assuming that you meant 120 dB of gain, which would lend itself
to a couple of MC1350s.

A 120 dB dynamic range rx would probably have little or no chance of
happening with something like what the MC1350 is in terms of IMD
performance and NF.

With regard to the post filter gain in the tx path, note that the
MAR amps are not very efficient and not all that swift for IMD
performance. Those are compromises inherited from the heavy feedback
that makes them so well behaved for gain flatness over frequency,
which has little or no utility in a narrow bandwidth application
like a post filter IF amp in the tx path, especially down at HF. A
single stage of your own feedback amp would allow you to set the
current for a wide range of output intercepts. The latter is not an
option with any of the MAR amps. The MAR amps are great for
applications requiring small foot print and very generic
repeatability, neither of which is a requirement for most homebrew

Risk Campbell, KK7B, does like the MAV-11 as a simple and quick semi-
low noise LNA "pill" for UHF and uW front ends. The NF benefit of
the MAV-11 would not be all that relevant for a post filter amp in a
tx path.

As for the gain between the SSB modulator and the xtal filter, that
will depend on what kind of modulator it is.

A diode ring with -20dBm of audio into it (for good IMD performance)
will leave you with about -26dBm out. The 2dB to 8 dB of filter loss
will then leave you at -30dBm on the low side.
So maybe another 16dB of gain either before or after the filter, to
offset a 6dB pad you will want to offer a broadband 50 ohm
termination for a tx IF amp gets you back to the -20dBm level for
the tx mixer input.

A Gilbert cell mixer will offer gain instead of the diode ring
loss,so that would reduce some of the gain needed in the tx path.

So yes, you are right that there isn't a need for a lot of gain
between the modulator and filter.

Bottom line here is try to keep you diode ring signal power to -
20dBm or less. Input powers of -10dBm or higher will offer you all
kinds of IMD and mixeing spur issues that can be horrible to figure
out without a good spectrum analyzer or serious "old school"
diagnostic techniques.

No need to make your task any more difficult than it already is.

As for AGC to the front end, that sounds like a serious challenge to
me. The issue to think about inthis regard is that your AGC
detection will be happening after the xtal filter. The time delay
(or phase delay, if you like to think of it that way) is a lot in
the context of the real time nature of what is happening in the
system receive path. So your system will not know that a large
signal is present until long after it has overloaded the first stage
(s) of the receive path.

EMRFD does cover this issue to some extent. I just don't remember
what page.

You might get some use out of some home brew pics I have posted at

There is a WA7MLH link at the top of the page.

I also have some youtube video(s) via username wa7mlh
Look for band imaging.

Hope this helps

1424 2008-02-07 20:22:30 Allison Parent Re: IF module