Collins Mechanical Filters

[W9LCE]

Frequently Collins Mechanical Filters come up on E-bay.

Is there any listing that will show me which do what?  AM/SSB/CW? -  what frequency they cover and possibly what bandpass they posses?  They are usually given by their Colins Code - which I have no idea what it means.

[VE3AJM]

Great information from WA3KEYs site

http://www.wa3key.com/filters.html

And here

http://jlkolb.cts.com/site/MFid.htm

Al VE3AJM

[N2DTS]

I like these better then the old mechanical filters:
http://www.kiwa.com/kiwa455.html
(The standard filter modules)

They used to come in almost any bandwidth, but I think the choices have been reduced, but they work VERY well in anything with a 455 KHz if, and are very easy to put in line.
Almost sdr good.

[WBear2GCR]

There is no difference between SSB, AM or CW as far as the filter itself is concerned.

More or less what matters is the center frequency and the bandwidth (also the skirt shape and depth).

One thing to keep in mind is that AM needs 2x the bandwidth for the same effective passband as does an SSB filter.

So, a 3Khz wide SSB filter would need to be 6kHz wide for the same bandwidth in AM. So, if you wanted 6khz AM you'd want a 12kHz filter.

The other thing to be aware of is that some of these mechanical filters have degraded over time due to the synthetic foam used internally - there is at least one webpage I've seen and maybe a video that shows opening up the rectangular filter case, cleaning the elements and putting fresh "stuffing" in... the ones that have degraded will not work properly. You can't tell from the outside. Apparently some have degraded, others not.

                   _-_-

[W9LCE]

Thanks

[WBear2GCR]

best check that... I'm not sure if they made upper and lower sideband filters or not, or if they slid the freqs for upper and lower to use the same filter. dunno, I seem to recall seeing some upper and lower filters?

the 75A-4 used only one filter for sideband, as I recall...

[Dave K6XYZ]

best check that... I'm not sure if they made upper and lower sideband filters or not, or if they slid the freqs for upper and lower to use the same filter. dunno, I seem to recall seeing some upper and lower filters?

the 75A-4 used only one filter for sideband, as I recall...

In the Collins Amateur line of radios.....they used a single 455kc mechanical filter and moved the BFO for USB/LSB.
Collins also slewed the PTO freq on USB with a switched in diode.
It works great when properly aligned.

These days.....don't buy any old filters....they have problems as described in earlier posts.
Today...INRAD makes great replacement filters....I have a few of them and they work much better than the original Collins filters that can be more than 50 years old these days....and for the older bathtub or round filters for the A3 and A4 receivers.....well...yikes. A good 75S-3B is far, far better.....and does not need mods to make it work correctly.
The INRAD filters have low insertion loss so the receiver does not lose gain like with original filters.

[RolandSWL]

 I modified my Sony ICF-2010 by removing and discarding the original WIDE ceramic filter and trading places with the NARROW ceramic filter.
 In place of the original NARROW filter, I installed a KIWA potted narrow filter which required tapping into the 4.5volt supply and using Velcro to attach it the speaker magnet.
 Audio(with the KIWA) in the NARROW position was terrible, sock in mouth even on side band. Also the potted filter was VERY sensitive to vibration and microphonic. The top of the speaker location was far from the best spot, but, not much room inside the radio for an alternate location.
 I can't speak to their other filters as I have not tried them.

My two zloty, Roland..................

[WQ9E]

Collins made a lot of different mechanical filters, some of their SSB filters were intended for use with switched carrier crystals while others were designed as either USB or LSB or to be used as a pair in an ISB system.  The only dead Collins filter I have run across was one killed in a R-390A with a failed DC blocking capacitor.  I have quite a few Collins mechanical filters both in Collins gear and from other manufacturers that used Collins filters and I haven't had trouble with any of them.  I have several vintage Japanese filters that suffered from decomposing foam that I had to rebuild but all 4 worked fine after repair.  I wouldn't hesitate to buy a vintage Collins filter that fit my needs.

I did just pick up some low cost Russian military surplus mechanical filters that will be put on an adapter board for use in a 51J-4 awaiting restoration.  The filters look good when tested with with my signal generator and scope and I will soon know how well they work in the receiver.  These filters have tapped input and output transducer windings for use in either low or high impedance systems.

[N2DTS]

Unlike some other filters, the KIWA standard filter modules are very tight, I have 6 Kc filters in my homebrew receivers and if you have a signal just out of the passband you do not hear it at all.
Very sharp just like an SDR.

No microphonics in mine, but I run mine off about 15 volts (rectified filament power) and 4.5 volts may be a poor choice.

But like mechanical filters (or even better) they are very sharp filters, so if you pick a narrow filter, it will be very narrow, maybe good for ssb and cw...

I think one of the reasons my homebrew receivers outperform almost everything else I ever tried is the filters.
 

I modified my Sony ICF-2010 by removing and discarding the original WIDE ceramic filter and trading places with the NARROW ceramic filter.
 In place of the original NARROW filter, I installed a KIWA potted narrow filter which required tapping into the 4.5volt supply and using Velcro to attach it the speaker magnet.
 Audio(with the KIWA) in the NARROW position was terrible, sock in mouth even on side band. Also the potted filter was VERY sensitive to vibration and microphonic. The top of the speaker location was far from the best spot, but, not much room inside the radio for an alternate location.
 I can't speak to their other filters as I have not tried them.

My two zloty, Roland..................

[VE3LYX]

In the 80s I bought a NOS Collins mech filter from my brother's surplus store. I asked a former Collins design eng (my Dad) if I could put it in my TS830S for CW instead of the optional but not installed factory japan filters. He said while it was technically on the "wrong" side because the IF notch is movable it would probably work pretty good if I remembered that and tuned for it. It does and has been doing a fine job ever since. If I recall properly it even fit the holes in the circuit board. However I use it only on CW and when things are really bad.
don