Technical Topics > SDR - Software Defined Radio

SDR issue with new antenna (RSP2)

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~SIGINT~:
I highly recommend the SDRUno Cookbook. It has saved me many times, and still does.

The latest version is available on-line:
https://sdruno.nn4f.com/

And an older copy in PDF format is still availabe here for download:
http://n6pet.com/wp-content/uploads/2016/06/SDRuno-cookbook.pdf

Elf36:
Thanks. I just opened the link. I'll check it out after dinner.

RobRich:
Assuming it is not local EMI/RFI causing your issues, have you considered a different antenna deployment? An end-fed inverted-L could offer DX benefits, especially since you already have a decent horizontally-polarized antenna. An inverted-L would add vertical polarization into the mix.

Feed it at the base with your 9:1 transformer. Use a few short ground radials for the RF ground side, though alternatively you could opt for just a ground rod since it is only a receiving antenna.

Look here from some ideas on antenna length:

https://palomar-engineers.com/tech-support/tech-topics/best-hf-end-fed-antenna#:~:text=Suggested%20wire%20lengths%3A

You are not transmitting, so you can disregard the coax length recommendations. The designs linked above are using coax losses to mask impedance mismatch, which is not a huge concern for your receiving setup.


Back to the dipole idea, if you can not fit an "ideal" flat-top, then perhaps an inverted-v would fit? Again, that would get you a little vertical polarization as well.



If you do mind experimenting at little, you might find your MLA-30 preamp would work decently with a loop-on-ground antenna. Even just a 60' LoG should suffice with a preamp.

~SIGINT~:
I have 2 x Bullet-9LF (.02-30 MHz) matching transformers from Palomar Engineers and I like the units. I have 1 in service as and end-fed antenna and the second as a spare to experiment with. I am also using the CMNF-500 as the common mode noise choke. As mentioned, the counterpoise is optional as the Bullet uses the coax's shield as the counterpoise. You can see that specified in the "suggested wire lengths" table. What is not so apparent on the web site is that you have to install a choke at the "Minimum Coax Length" or else the entire length of the coax becomes part of the antenna and ultimately will bring noise into the receiver on the shield. The choke is shown in one of the diagrams. This is well detailed in the instructions that ship with the Bullet.

Elf36:
I've had more time to compare the antennas and definitely notice a difference now. I think the first compares were similar due to the fact that the signals were strong, such as AM broadcasts or time stations. Listening to ham radio or pirate stations show much more gain on the wire vs the MLA-30.

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