Crystal Filter Perfection

Sometimes, just sometimes, all your ducks align in a row and you build something that is dead set on the money. I think today I have done just that with this crystal filter.

Firstly I have redesigned the PCB board and test jig setup I am using, making construction just a little bit easier and allows me to easily use the slightly larger binocular core.

But secondly, I think i hit the nail squarely on the head, with this filter. I mean its almost perfect. 5dB loss, great, good shape factor, great, -55db stop band, great, exactly 2200Hz passband PRICELESS. I honestly could not have done better even if I tried. Now to build the receiver board and pray to Jebus that it works as good as this filter looks.

As a bonus, here is his friend the CW filter, 600Hz wide. A little more lossy but still good stop band and shape. I was shooting for 500Hz, bit I need maybe another 15pF per node. Good enough for me though, that is 2 filters for a receiver, 2 filters that should perform reasonably well.

Final EDIT:

So I was going to upload the gerbers and create a great big post about how to use them. But, i went looking for the files and it looks like I have deleted them by mistake when cleaning up my project files. I got no idea how I did that, but they are gone and its a lot of work to recreate them, so there will be no release of these PCB files. Lucky for me I can reorder them easily and I also have enough board here to make 20 filters, that should be a life times supply for me. Rather sad really, because they work so well.



Before and After.


While not entirely a necessity, I upgraded the crystal oscillator that I use when building crystal filters. It does the same thing just looks a little more fancy. HAHAHA, when it only costs $2 to throw a simple board like this onto an existing order, why now hey? 😉


5 Band Filter Board

Just like a bought one hey? This has been a while in the making and brings together many of the smaller project boards into one. We have 5 low pass filters, band pass filters, TX/RX switching, and + and – 20dB RF preamp. Low and behold, it actually all works right out of the box, no major issues, other than winding all those toriods is a nightmare LOL

In testing the losses were acceptable, 1/2 a dB on the low pass and 1.5dB on the band pass. With essentially 10 filters on the board, it was going to be interesting to see how much work they would require to bring into the correct band.

Most of the filters were actually just fine as you can see here with the 80m low pass filter. Only 1 low pass filter needs to have a turn taken out of each toriod to bring the corner frequency up a little so the corner is not in band, and 3 of the band pass filters need the same to move them up in frequency also.

I did my best to account for strays and variation in winding, but there is always going to be some error and fixing, especially in the band pass filters where I am using a specific value of inductance in the calculations for the filter and then using a turns calculator to get that inductance. These things are always rather hit and miss. With the low pass filters you can always set the corner frequency higher than needed, like with this 80m filter, our band here is from 3.5Mhz to 3.7Mhz, and I set the corner frequency to be 4Mhz, because if you end up with strays you always end up with more inductance and capacitance, not less and those lower the frequency response.

Anyway, thats it for me, I have another 6 boards to build now and I seriously hope that the receiver board is actually good, because if that works well enough to use, I will have a very useable and workable 5 band 50w transceiver. Wish me luck.


When Is A Newbie No Longer A Newbie?

So when is a newbie no longer a newbie? Like to be or not to be, that is the question and one that to me at least is rather interesting. You see, a few days back someone remarked to me that I am still a newbie. My initial thought was O’REALLY!, no, a newbie is not what I am, what I am is not soon to be deceased so to the old guys I just seem like a newbie.

For a start, I have been involved with ham radio since 2014. That’s 7 years. Think of your favorite sport, you have your rookie year then you become one of the regular players and after about 5th year you are considered a veteran and by the 10th year you are looking at retiring after hopefully a distinguished career and a whole slew of awards and accomplishments.

With ham radio, I think its more an US and THEM mentality being shown by some, and yes its some, not all, where you are always a newbie unless you are one of them and a 30 year veteran. Where as for me, I do not give to craps about how long you have been a ham. To borrow from Martin Luther King, i do not judge by how long they have been a ham, but by the content of their character. There are 30 year newbies out there and 1 year veterans, what matters is what one brings to the table, not the duration they have been sat there.

While I am no newbie, i am also no veteran either though my list of accomplishments is growing. I have worked DXCC, placed well in some big contests, scratch build a few transceivers and used them to make contacts, partaken in awards schemes like WWFF and received multiple awards, was DXér of the year in 2016 as an Fcall and have even turned my hand to elmering a few people in electronics until they found their feet and no longer needed my help. That is certainly not all of the things I have done and its certainly not the resume of a newbie and its a lot more than some veterans out there.

There is always someone to learn from out there, even those real newbies can have a perspective that might just change your world view, if only you are open minded enough to actually listen to them, rather than jump to conclusions that newbies are all dumb.

Baxter Out.