How to assemble a narrow CW filter for your Yaesu FT-817/FT-818/FT-857/FT-897 (an affordable YF-122C equivalent) readers know that I’m a big fan of the venerable Yaesu FT-817 and FT-818 series transceiver.  So much so, I own two FT-817NDs–I purchased a second unit last year primarily for full duplex satellite work.

As I mentioned in a previous post, the one gotcha with the FT-817 and FT-818 is narrow CW filter availability. The YF-122C 500 Hz and YF-122CF 300 Hz Collins filter boards are no longer produced. Neither are the Inrad equivalents.

With the renaissance of CW we’re experiencing along with the growth of POTA, WWFF and SOTA, narrow CW filters for the FT-817/818 are very difficult to find and come at a premium when you do find them. I saw one sell recently for $250 US–over double what I paid two years ago.

In addition, this same filter not only fits the FT-817/818, but I believe it also fits the popular FT-857 and FT-897 series transceivers (please correct me if I’m wrong about this).

The Problem: I wanted another narrow CW filter

One of my FT-817NDs is loaded with a Collins 500 Hz mechanical filter that I purchased from my buddy Steve (WG0AT) nearly two years ago.

The second FT-817ND had a narrow Inrad 2 kHz SSB filter that came with the radio when I purchased it used (see image above).  Initially, I had no intention of buying yet another narrow CW filter because I’d only planned to use the second unit for FM and SSB satellite work.

Then, during field day this year, I decided it might be fun to build a quick-to-deploy portable HF station with something like an Armoloq TPA-817 pack frame. That thought experiment made me realize that I should simply bite the bullet and get a narrow CW filter for the second FT-817ND.

I started searching in late June and was simply not willing to pay the price for the very few filters that have shown up on the the used market.

The Solution? Assemble one!

I owe QRPer reader, Petr (OK1RP), for this tip.  Thank you, Petr!

The process of assembling your own narrow filter is actually quite simple and affordable. If you have even the most basic soldering skills, you’ll be able to manage this easy project. If interested, keep reading and I’ll show you how you can assemble your own…

Contact Artur (SP6AB) and ask to purchase one of his FT-817 filter boards

Artur makes these filter boards in small quantities and will configure them for the Collins 526-8693-010 500 Hz filter. This requires adapting boards he originally designed for a different Collins filter, so he must cut a trace and add a few extra components. Because of this, the lead time is typically one week.

Artur charges a very reasonable $10 US for the board and $5 US for shipment via registered letter from Poland. Artur does this as a service to his amateur radio community; he could obviously charge much more. What a great fellow.

I received my filter board within two weeks of it being shipped.

Contact Artur at the following email to confirm pricing and availability: [email protected]

Make sure to tell Artur the actual Collins filter part number you’ll be using so he can configure the board properly.

Purchase the Collins narrow CW filter

You are looking for the 7 pole Collins 526-8693-010 (AOR MF500) filter.

There are a number of eBay sellers offering these filters–most are located in Japan. Prices range from $103 – $160 US, but the majority are less than $125 US.

I purchased my 7 pole Collins 526-8693-010 (AOR MF500) from this seller and paid about $108 US shipped.  Shop around, though, as there are many sellers offering this filter (double-check the part number prior to purchasing because eBay will often show results for similar part numbers). I chose this particular seller because they offered free expedited shipping and a 60 day return window. They also had 100% positive ratings. I received my filter via FedEx within 2 weeks of purchasing.

Click here to search eBay for a Collins 526-8693-010 (partner link).

Finally, solder the filter to the circuit board and install it

Note the tree soldering points on the bottom of the filter.

This bit couldn’t be easier.

Since Artur essentially does all of the hard work on the board, all that is needed to mount the Collins filter to the board is to solder it in three spots.

The process will take a max of one minute once your soldering iron is hot!

I used a bit of tape to hold the filter to the board to solder the first leg of the filter.
Close up of the three solder points on the bottom of the board

Here’s how the filter should be oriented looking at the top of the board:

[Update: Artur has made a slight change to the filter board design. It’s still intuitive, but if you would like to see the new board, check out KM1NDY’s blog post and images and also photos by Steve (MW0SAW) at the bottom of this post.]

Finally, mount the new filter board in your Yaesu radio. This board simply slides onto pins inside the radio. Take your time to properly align the pins so that the filter boards sits properly.

Here’s the location in the FT-817ND:

Next, you need to tell the radio that you’ve installed the narrow CW filter board by going into menu item “38 OP FILTER” and selecting “CW.”

Before putting the cover back on your radio, I suggest testing to make sure the narrow CW filter works.

Hook your antenna up to the radio and activate the narrow CW filter from the quick menu.

It was rewarding to hear the 500 Hz filter engage. I was lucky in that a CW contest was in progress, so could quickly hear the improved results using the narrow CW filter.

So pleased with the results!

Again, I’m most grateful to Petr for pointing out this affordable filter option and for Artur to offer his modified filter boards at such a reasonable price.

I paid a total of $123 which I feel is money very well spent and much, much less than the inflated prices we’re currently seeing for the Yaesu YF-122C on the used market.

Now I need to revisit the Armoloq TPA-817 pack frame idea.

Update: New filter board

As mentioned above, Artur made some slight modifications to his filter board design. If you’ve ordered one recently, it might not look identical to the ones in my photos. Steve (MW0SAW) kindly provided the photos below of his filter install. Thanks, Steve!

Thank you!

Thank you for reading this how-to article. I hope you found it useful.

Of course, I’d also like to send a special thanks to those of you who have been supporting the site and channel through Patreon and the Coffee Fund. While certainly not a requirement as my content will always be free, I really appreciate the support.

Thank you so very much!

Cheers & 72,

Thomas (VY2SW / K4SWL)

32 thoughts on “How to assemble a narrow CW filter for your Yaesu FT-817/FT-818/FT-857/FT-897 (an affordable YF-122C equivalent)”

  1. Hi Thomas! Yes, these filters would fit an FT-857 and 897 (there are room for two of them at the same time) and they are a must for CW, as they come with a 3kHz-ish wide filter by default.

    For the 857 and 897, you can use the digital filter, but it works in audio frequency so the AGC is affected by nearby signals (I think the term is ‘swamping’).

    One trick for the 857/897 CW: engage the DBF filter, disable the AGC and reassign the RF Gain to the Squelch control. Then lower the RF gain a bit to reduce background noise. This way the AGC is not affected by nearby signals and the audio DBF works fine with a stable volume. If nearby signals are very strong, further reduce the RF gain.

  2. Great solution to a ongoing problem with a great rig! Tough to op without it. Thanks to Artur (sp)? Supply and demand has made these filters over priced for sure.

  3. Thomas, a most interesting article; I wasn’t aware of the cost of the filters as I have both for my original 817. This does look like a superb solution though. It’s also tempting me to dust down the ‘817!

    Richard M0RGM

  4. This is cool, Thomas. I recently went a different route.. I have a new to me 703 with the 500 Hz crystal filter, but I wanted a bit more of a narrow filter when I need it. I ordered and built a Hi-Per-Mite kit from 4 States QRP group (installed in an Altoids tin and powered by a 9v battery, total cost was $30). It works really well as a small external filter with with the 703, and also on my old TS-520 (also with a 500 Hz filter). Bonus is that it offers a bit of amplification, too, even built in it’s stock 0dB configuration, so it helps with some of the weaker signals on my QCX mini.

    1. Oh, forgot to add: the Hi-Per-Mite is a 200 Hz filter, and the same circuit is used for filtering in the QCX, so I knew I liked the sound before buying.

  5. Thinking that over the next year or two I want to upgrade my license to include CW, I’ll need to also improve the CW capabilities of my FT-818. This is the answer! Thanks to Thomas and the board maker Artur for this. Will start eBay hunting for the filter.

  6. A few years ago I got and installed the Collins Cw filter. In my ft817. Was a most needed accessory.

    I don’t use my ft817 now that I have a IC705. If I sold the FT817 bet could remove the filter and sell separately and get more.

    Collins spent a lot of effort making these filter. Took a 30 day process. I do have one in my 75S3 rcvr also.

    73 Ron n9 we

  7. This isn’t about building a filter, but an adapter board touse a different filter.

    And the ongoing problem is that Collins stopped making mechanical filters. Some Japanese company made them in the sixties (you could buy them at Lafayette Radio, which also used them in some equipment), but that seems in the past.

    So it’s always about scrounging a filter from somewhere.

  8. Great article Thomas.

    Earlier this year I had the chance to obtain the correct filter which was on an FT847 filter board (filter had same serial number) so could have done as you did, sadly Inrad ran out of their stock of FT817 boards before I had a chance to purchase one.

    However I was lucky enough to pick up a Yaesu ft817/8 500hz filter earlier this year at a reasonable price so am very happy but I think the lack of filters is one of the big drawbacks of the 817/818 series.

    As an aside four years ago I traded in my 2001 FT-817 for a TH-D72 to work the FM satellites. In 2003 I purchased an Expanded Spectrum System 500hz filter for the 817. When I traded the 817 in I forgot the filter was in the radio.

    Now that I am enjoying CW I kick myself for being so stupid to leave that filter in the 817. I should have kept it in a drawer for future use!

    1. I was the one who purchased the last Inrad board in early 2022. I checked a day after I placed my order and the ordering link was no longer available.

      Sorry….well, not sorry. 🙂

      Glad you were able to get a filter, though!

  9. A bit wandering off..
    The HiPerMite is indeed a good solution, I use widely on Boatanchors and vintage stuff such as Drake gear.

    I found the 0 dB purported gain nonetheless has me reduce the AF gain on receiver when HPM is deployed.

  10. Hi Thomas:
    I found your blog post while trying to track down a filter for the 818 not surprisingly! As new as I am to CW, the first time I tuned into lower parts of the HF bands, I was shocked to here all of the CW tones bleeding together… I am spoiled by the modern rigs I own! In any case, I purchased one of the filters and just made inquiry to Artur about the purchase process. Fingers crossed I can make this all work! Thanks for the tip!


  11. Thanks Thomas! I had been hoping for a reasonably priced filter for a long time but wasn’t too keen on the SOTABEAMS board. I did this and it’s a whole new radio at a more reasonable price. BIG thanks to you and Petr!

  12. Does anyone have any history about the Collins filter? If they’re “unobtanium “ then why are all these “Collins” filters now available? Is someone manufacturing the base filter unit and we just need a base board to make them fit in our Yaesu radios?

    Luckily I had W4RT completely trick out my 817 20 years ago and it still sits proudly on my side bench.

    1. Where they are available? Just few old stock items are obtainable thru eBay from some distributors. Luckily these items dedicated for AOR receivers fits to our Yaesu radios with appropriate PCB…

  13. Hi Thomas, do you think that the 500Hz is narrow enough for field day? I can’t remember what I used on my KX2 this year.

    Also, how does one submit guest posts?


    1. Hi, Auston,

      I think Field Day or any other popular contest is about the only time I (personally) would use a 300 Hz filter. It could be very useful especially if you’re the sort of person who really likes narrowing down a filter to hear only one contact.

      Most of the time, I find 500 Hz to be the right narrow option for me. Even on Field Day, I’m unlikely to narrow a filter much more than 500 Hz because I find the audio more pleasant over long sessions.

      Thing is, it’s a very personal preference and you really can’t go wrong either way. 🙂 For POTA and SOTA, if you have a 300 Hz filter engaged, it’s possible you could miss some contacts who are just slightly off frequency. Their signals might be attenuated.

      If you’d like to submit a guest post, just send it to me in a Word document (or text doc) with photos attached separately. Just note where you want your photos in the doc and I’ll format it!

      K4SWL / VY2SW

  14. Hi Thomas,

    FYI I have an Oak Hills Research Switched Capacitor Filter SCF-1A from years ago. Works well when no IF filter available in old school rigs.

    I installed INRAD CW filter in my FT-857D and CW & SSB filters in my FT-847 years ago too. They make all the difference.

    Good job on your filter install!

    73 Kevin N2TO

  15. I sent Artur and email about a week ago but still haven’t heard back from him. I hope he is still providing these boards.

    1. You might try contacting him from a different email. Perhaps his SPAM filter caught your message–mine doews this all of the time completely at random it seems. I know he’s actively replying to people now.

      1. I did get hold of Artur and he’s indicated the boards I ordered have been sent. I’ve already acquired 2 filters on eBay.

  16. I’m not sure what I did wrong, but I get a lot of attenuation when I engage the filter – to the point that weak signals disappear even with RF gain all the way up. Works great on strong signals, but mostly useless due to the attenuation.

      1. I have a newer board from SP6AB (like in the pictures appended to the end of this article) and the filter can only be attached to the board one way as far as I can tell. My finished filter looks just like the ones in the pictures above and is installed in the rig just as pictured in this article.

  17. Followed this advice and received first class service from Artur. Scavenged the required filter from one on an FT1000 filter board I found for sale on the devil’s bazaar. Just need to be sure about the part number which I checked with Artur before hitting the buy button. Initially it didn’t work in my 818 but after an hour checking out the circuit for faults a Google search pointed me to some fool who had mounted the whole pcb upside down in his 817. Yep I had done the same thing ! 10secs to turn it over and all was fine.

  18. I just built two 500 Hz filters using Artur, SP6AB, boards. One was from the AOR stock, the other was salvaged from an FT-1000MP filter board (larger board, does not fit FT-818). Both work great! The AOR filter has a number 526-5693-010 and the one from the FT-1000MP is 526-8686-030. They both are 500 Hz, 7 pole mechanical filters and they both work in my FT-818. The supply of the bare filters has recently dried up and is quite challenging to find the bare board. The ones I’ve seen on eBay are going for around 300 USD!!! Good luck in your quest to find a filter these days. As I type there are a couple on eBay on FT-818 board for 300 USD. (2/23/2024)

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