Nick M0NTV demonstrates the design, building, testing and tweaking of a 15m Band Pass Filter. Hans Summers' Band Pass Filter build instructions can be found here: qrp-labs.com/bpfkit.html
Thank you for another great video. It was both great learning for the intended purpose as well as getting over the "terrifying fear of failure" when winding toroids.
I’ve been a fool! I’ve gone and passed up constantly on those adjustable capacitors. The big big ceramic and metal ones?! I want to sink my head into the sand like an ostrich now when I see how much those baby’s fetch on eBay…. Hey?!? Your schematic there? It looks like the sort of circuit that goes between mains and transformer inside those ‘power conditioners’!?! ‘Common mode rejection’ - ahhhh I’m beginning to learn a few things here!! Edit: I absolutely love your ‘through hole components’ surface mounted to your copper clad board - very smart way to go while you’ll be presenting your board on camera. It looks great!
wondering now about perhaps shaping curves into the strings of an electric guitar to add an adjustment layer. kind of like an eq with strings and pegs 😂
George was such a great inspiration to so many people - myself included. I'm sorry I never got a chance to meet him myself. I do still study his designs though and his enthusiasm was infectious. Thanks for watching. 73, Nick
Hi Nick, great video as always. I have watched your video and read Hans Summers' document. I have mocked up a circuit in LT Spice but when I look at the trace V004, all I get is a flat line. As far as I can see, other than component values, my schematic is the same as yours in LT spice. Any suggestions or advice? I am new to homebrew and LT spice (sigh).. Thanks again!
Hi Ryan, without looking at what you've done it is hard to comment. What I would suggest though is try an LTSpice simulation with my values for my frequency range. It might help to narrow down where the issue is. All the best to you. 73, Nick
Hi there! I think you mean toroids rather than ferrites - as these are not ferrites they are iron dust cores. But I know what you mean! To be honest the insertion loss is so low with these kind of filters (mine are typically less than 1 dB) that for HF frequencies it is probably not worth worrying about. Once you get higher in frequency then I agree - the inductors get smaller, the losses get bigger and air-core is a much better option. Thanks very much for watching and commenting. 73, Nick
@@M0NTVHomebrewing yes. I was using ferrites in a generic sense to cover any metal.powder. but do you really think a dB of loss is low? It adds directly to noise figure in a receiver and sucks power from a transmitter.
I take your point but to be honest when you are building from scratch manhattan-style you will inevitably introduce losses all over the place. The only real question is how much loss are you prepared to live with? Your mileage may vary, as they say. Thanks again. 73, Nick
@@M0NTVHomebrewing You're right. But my recent history has been 30GHz transceivers for space use. In that situation, even 2mm of pcb track from the antenna probe to the first HEMT FET introduced unacceptable loss. The probe need retuning to be a noise match to the FET with direct connection. Mileages do indeed vary.
You make & Tune Excellent filters.....The Actual sweep run to Model is 'bout as Close as it gets !! .....Just for Educational & Practically purposes, Maybe you could Make an Identical Filter using hand wound #14 or 16 wire gauge Air Core inductors (Instead of Toroidal core) & show the sweep run loss Differences if any.....I almost Always have a usable piece of Enameled magnet wire around the shop & almost Never have the Correct Size & ferrite Mix type thats needed & probably Most of us beginners get initially Better results & feel more Confident winding Simple cylindrical Coils.....
Thanks Tom. Depending on the frequency you wouldn't be able to practically use an air-core coil. You could for VHF but for HF they would have to be pretty big in order to get the required inductance. Best idea is to stock up on type 6 yellow iron dust toroids (T37-6, T50-6). This will tackle 30m and above. I'd probably then use type 2 red (T37-2, T50-2) for 160, 80, 60 & 40m. Air-core coils are useful in filters where you need very small amounts of inductance though. 73, Nick
Was just wondering how much power your bandpass filter is capable of handling? The design looks like it would be perfect for Field Day filters here in the US. 73 AE3D.
Hi Keith, the one in the video will be good up to about 20 watts or so. It depends on the toroid type you are using. If you look inside a commercial rig rated at 100W output then you won't usually see huge toroids - probably T50-6 for the higher HF bands. Having said that for my Shelf-17 rig which puts out 80+W on 17m I used T68-6 just to be safe! Your mileage may vary as they say. 73, Nick
Thanks. If you look at my final comparison between the LTSpice simulation and my sweep on the Spectrum Analyser then you can actually see for yourself. It is a sweep from 15 - 30 MHz: each horizontal division is 1.5 MHz and each vertical division is 10dB. You'll find it at 32:15 in the video. Basically 20m is nearly 40dB down, 17m about 20dB down and 10m about 30dB down. Hope this helps. 73, Nick
Hi Michal! Yes, it's a tried and trusted design. You can use different designs and possibly get steeper skirts though. Check out Bill Meara's experiments on the Soldersmoke Blog and the Soldersmoke RU-vid site. I tend to stick with these simple double tuned circuits though.
I'm planning on getting my ham license and I'm already into ee as a hobby. The only piece of gear I don't have for all this is an sa. I'm planning to buy a siglent. Is the plus model worth the extra money for the mod I read about on the eevblog website. Also what are the names of those good variable caps you have? Great content my friend. I'm new to rf but it seems like the logical path to follow and a great hobby.
Hi there! Thanks for watching. I've not done to mod to the Siglent so I can't say about this but it is a tremendous piece of equipment. That said, you can also get a long way with a Tiny SA these days. The variable trimmer caps are like these: www.ebay.co.uk/itm/284572247234?hash=item4241d3e4c2:g:JMwAAOSw4hRhvG2z&amdata=enc%3AAQAIAAAA8A8n5ZoK6A0Nd%2FkE4Z6RL71zssBh0Gf%2FIW5utLhXQZ15HLlCtZV6CbQCNQoPhp%2FnjGtdFZrwaqfmY3KqtbAuCt%2FJ0clywg8ACMGgiNpyKDOt201FLOrqjmtFbCa40XD6znc4gVIoT7GOUdpVuU0jli3evXFyhVyOkf%2Ft74T1eRHAlkSlIxn2xM7q0BIMMn5w4CsENH8veQBkpUDyptHH7D%2BUecx%2Bk0gozs3Y2HXajwvZHvcD06fqXPI2w2y7jHZMii4RXq0QBz06V7s8qi6U9KiT9WsLhrt6WXV2zDlh9fho0V%2FVtsFS55iIgxUsA9o9uw%3D%3D%7Ctkp%3ABk9SR4LN5o-bYw All the best as you go forward into Ham Radio - it's a great hobby! 73, Nick M0NTV
Hi there! I don't attempt to measure the Q of my inductors in band pass filters. I've found that all that is really necessary is to build them as carefully as possible. Being able to measure them is useful (I use a Peak Atlas LCR45 meter) but even then you'll need to tweak them by adding or subtracting turns or by separating or compressing them. Once you've got them exactly where you want them and the filter is complete then it is good to fix them with glue, wax or whatever so nothing moves around. In terms of buying the toroid cores then I usually use a few trusted sources e.g. Club Sales at the GQRP Club or www.sotabeams.co.uk Hope this helps. Thanks for watching. 73, Nick
Thanks very much. You can certainly use your NanoVNA but you just have to remember that it is expecting to 'see' an impedance of 50Ω. Personally I'd wind 11 turns primary (1.5KΩ end) and 2 turns secondary (50Ω end) on an FT37-43 and then measure the impedance (smith chart & SWR). This should be fine on RX or TX - assuming the next stage has a 50Ω impedance of course. Hope this helps. 73, Nick
My primary is 50ohm (antenna), the secondary is 1500 Ohm (input of NE602). I am using a similar pass band with with Toko coils. Are you saying that the S11 port of the nanoVNa needs to see 50 ohms? If so, I will place the primary on that port and the 1500 ohm side on the S21 port? will that work?@@M0NTVHomebrewing
Hi, sorry but I'm not really sure what you are trying to measure. Both ports of the NanoVNA expect to see 50Ω. In my last comment I described an impedance matching transformer to connect your NE602 (Z=1500Ω) to something else (e.g. band pass filter, antenna etc) with Z=50Ω. You can tell how well you have matched this by doing an S11 measurement on the 50Ω end of your transformer. You'll be reading (Smith chart and SWR) how much signal is going through and how much is being reflected back because of impedance mismatch. 73, Nick
Correct - although theoretically there is such a thing as a "lossless" transformer in reality you'll never build one. The practical reality of building a transformer means there will be some losses. These losses needn't be huge though. As long as you build them as carefully as you can you should be fine. Happy toroid-winding! 73, Nick
Hi Mikele, band pass filters are always a trade off between 2 properties: (1) the bandwidth of your filter and (2) the insertion loss of your filter. The narrower you make the bandwidth the more insertion loss you're likely to get. It also works the other way of course: a wider bandwidth = lower insertion loss. So it is always something of a compromise. Having said this I've build many of these for 80m and had no more than 1 dB IL. Using good quality trimmer caps helps - as does careful construction of your inductors. I made another (earlier) video on this which might be of interest: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-dZnvpxVd7dc.html (NB. Make sure you read the description about the error in the onscreen schematic!). Hope this helps and all the best to you. Keep going! 73, Nick
Hi there! The best advice I can give you is to refer to Hans Summers' instructions (which I have linked to in the description of this video). If you're feeling adventurous and want to design your own then I find a filter design simulator very useful. One of my favourites is markimicrowave.com/technical-resources/tools/lc-filter-design-tool/ Hope this helps. 73, Nick
@@M0NTVHomebrewing Thanks alot for your answer! I tried to recalculate and I realized that if we use both Cap (23pf and 30pf) we would get nearly 21Mhz. My question is now that could I get FM signal with this SSB receiver?
You might be able to listen to some FM signals using the slope detection method (google it!) but if you are serious about FM demodulation then really that requires something of a redesign. FM is a fascinating thing but it is a whole different form of modulation and so requires a different approach. 73, Nick
