Message	Date	From	Subject
11777	2015-10-13 15:00:37	John Lawson	Re: emrfd] QST SA 110MHz bandpass filter nearly complete but I have
Vince,I used #18 wire for my coils.....check you wire size as one of the troubleshooting steps.......Finally, I worked with the coupling wires and the piston cap adjustments until I arrived at the proper shape of the filter as shown by a sweep of the filter, then I could get a good look at the inserti
11778	2015-10-13 17:07:41	Phil Sittner	Re: emrfd] QST SA 110MHz bandpass filter nearly complete but I have
Vince- I second John’s comments. My unit has an insertion loss of 5dB as well and was a snap to calibrate. Over coupling leads to the double humps you have but I don’t know how that impacts the insertion loss. Use of larger wire improves the Q of your inductors and lowers the loss. The easy way to deal with the coupling is to use a longer length than specified and then trimming each of them in small increments (equally) until you see the bandwidth expected. If you trim too much it’s not expensive to replace the wire. This filter was for the original SA design. I also just finished building Ashar’s configuration but found better return loss with the w7zoi approach using the piston trimmers and 18 gauge wire. Phil Kd6rm Sent from Mail for Windows 10

Vince-

I second John’s comments. My unit has an insertion loss of 5dB as well and was a snap to calibrate. Over coupling leads to the double humps you have but I don’t know how that impacts the insertion loss. Use of larger wire improves the Q of your inductors and lowers the loss. The easy way to deal with the coupling is to use a longer length than specified and then trimming each of them in small increments (equally) until you see the bandwidth expected. If you trim too much it’s not expensive to replace the wire. This filter was for the original SA design. I also just finished building Ashar’s configuration but found better return loss with the w7zoi approach using the piston trimmers and 18 gauge wire.

Phil

Kd6rm

Sent from Mail for Windows 10