bluetail 700 filter

[kb5udf]

I have had the chance to test the bluetail passive 700mhz filter from my home shack and find it useful. I hooked it up to the same tower discone as the the screenshots from the 700/800 filter. I am using the same airspy, but I increased gain to 13, but that appeared to give optimum SNR.

 

[maus92]

That is excellent performance by the filter, but that bleed over from Band 14 really sucks. I have a very sharp drop-off starting at 768. I'll try to grab an image of the situation at my office - any idea of the filter's insertion loss? It would not matter much for me since I am located well within the site's service area.

 

[FreqNout]

@kb5udf thank you for testing both of Todd's prototype BANDPASS filters on multiple rigs and locations. Very positive results that allow your radios to work again.

@maus92 this may help answer your question

The second (passive) 770 filter is on the way to you. That filter will give better stop-band attenuation, but you will lose some sensitivity unless you place it after the SELECT-78 filter/preamp. Either way, it looks like both solutions will work for you. I think the "final" version of the passive filter will end up being ~3 dB of insertion loss. That is not a bad trade-off if it gets your receivers working. Even though there appears to be very little interest in the filters now (possibly due to the off-topic posts), I understand that demand could grow. I'm not going to invest in more parts until we see how the new MicroP25RX-II design goes. That will determine the future of BTT.

 

[kb5udf]

3db give or take seems about right from my guesstimate. My plan for the filter, is to again put the p25rx (now with filter) back into my glove box and monitor the LWIN site I am in the footprint of 99 percent of my driving time, same as I did before the invasion of the band 14 noise. The Bluetooth streaming to my truck’s audio system works great as it shows the alpha tags. Happy days are here again.