Slightly offset IF cans - UK Vintage Radio Repair and Restoration Discussion Forum

kellys_eye · 14th Dec 2022, 3:58 pm

I'm considering experimenting with a 4-tube station design (73 magazine, August 1971) which principle image rejection is based on the use of a 1.7MHz IF.

I've heard of a 1.6MHz IF (Denco did a range I believe) and presume such IF's will readily tune (even if a padding capacitor is required) to 1.7MHz but I ponder the original use of 1.7MHz in the first place - I mean, is this an IF that has a history of 'normal' use? It's not as if I've ever seen that frequency in second-hand sales or even seen it in any domestic/commercial stuff. Maybe my world is limited in that respect?

The construction article makes no special mention of the 1.7MHz IF - as if it was something used every day - which I somehow doubt.

G6Tanuki · 14th Dec 2022, 4:04 pm

The US AM broadcast-band is 535-1605 kHz.

So there's a risk that using a 1.6MHz IF could get IF breakthrough. 1.7MHz IF avoids it.

Cruisin Marine · 14th Dec 2022, 4:43 pm

The US AM broadcast-band is 535-1605 kHz.

So there's a risk that using a 1.6MHz IF could get IF breakthrough. 1.7MHz IF avoids it.

In recent-ish times the US band has been extended up to 1.7 MHz for lower power broadcasters, they should not be a problem in the UK or Europe though.
Here is more on the stations on the "X" band https://mediumwave.info/2020/10/10/am-x-band-stations/

There are are, however stations on 1710 kHz in Norway and Sweden I have just noticed http://www.mwlist.org/mwlist_quick_a...rea=1&kHz=1710
There is also 1701 kHz Portugal, and maybe many more. A comprehensive list is here. http://www.mwlist.org/mwlist_quick_and_easy.php

14th Dec 2022, 3:58 pm	#1
kellys_eye Octode Join Date: Jan 2014 Location: Oban, Scotland, UK. Posts: 1,129	Slightly offset IF cans I'm considering experimenting with a 4-tube station design (73 magazine, August 1971) which principle image rejection is based on the use of a 1.7MHz IF. I've heard of a 1.6MHz IF (Denco did a range I believe) and presume such IF's will readily tune (even if a padding capacitor is required) to 1.7MHz but I ponder the original use of 1.7MHz in the first place - I mean, is this an IF that has a history of 'normal' use? It's not as if I've ever seen that frequency in second-hand sales or even seen it in any domestic/commercial stuff. Maybe my world is limited in that respect? The construction article makes no special mention of the 1.7MHz IF - as if it was something used every day - which I somehow doubt.

14th Dec 2022, 4:04 pm	#2
G6Tanuki Dekatron Join Date: Apr 2012 Location: Wiltshire, UK. Posts: 13,998	Re: Slightly offset IF cans The US AM broadcast-band is 535-1605 kHz. So there's a risk that using a 1.6MHz IF could get IF breakthrough. 1.7MHz IF avoids it. __________________ I'm the Operator of my Pocket Calculator. -Kraftwerk.

14th Dec 2022, 4:43 pm	#3
Cruisin Marine Heptode Join Date: Jul 2018 Location: Worthing, West Sussex, UK. Posts: 992	Re: Slightly offset IF cans The US AM broadcast-band is 535-1605 kHz. So there's a risk that using a 1.6MHz IF could get IF breakthrough. 1.7MHz IF avoids it. In recent-ish times the US band has been extended up to 1.7 MHz for lower power broadcasters, they should not be a problem in the UK or Europe though. Here is more on the stations on the "X" band https://mediumwave.info/2020/10/10/am-x-band-stations/ There are are, however stations on 1710 kHz in Norway and Sweden I have just noticed http://www.mwlist.org/mwlist_quick_a...rea=1&kHz=1710 There is also 1701 kHz Portugal, and maybe many more. A comprehensive list is here. http://www.mwlist.org/mwlist_quick_and_easy.php __________________ "Behind every crowd, there's a silver Moonshine" Last edited by Cruisin Marine; 14th Dec 2022 at 4:48 pm.