My LimeSDR HF Project

Here is my LimeSDR HF project.

I’m after a bit of advice.

My question is whether to pad the output from the Lime into my amp or not.

This is my amp

It wants a 0db input. Problem is the Lime has a wide power output on the HF range. Opinions on how to deal with this ? Perhaps I could not pad the output form the Lime and control the power output in software … reducing it as frequency increases.

I also use this switching board

It has a BPF loop available. Is anyone familiar with the board ? Does the BPF apply to both TX and RX ?


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I scored a 1-128 Db attenuator. It should keep the output even. Doing HF/VHF/UHF with the PA/filters from an 857d.
Going to all be controlled by an Udoo X86 ultra that has onboard Arduino.


Yeah cool. Mine is going to be remotely mounted (on a hill top at 1400 feet) and controlled by a mini PC so I can’t easily control stuff like variable attenuators. I’ve just got an inline attenuator. It’s either in or out.

Still looking for low pass PA filters for my setup. I think I’m going to trial it as RX only for a while and move to TX after Xmas.


The attenuator will be controlled by the Arduino that is built into the Udoo. It will be doing most of the RF controls.
If you know hams, find a broken ham radio for the bands of your interest. Filters are usually on separate boards on older radios. TS-440 has a great LPF board. It’s bandpass filters can be dremeled off the main board & all controlled by BCD codes. It’s better to use something that was all engineered right & ready to go.


I’ve got an FT 757 but its still in good working condition so won’t be taking anything from it. I see a few cheap LPF kits on eBay that should do the job.

I’m using IP controlled relay box for all my switching. I guess Arduino is a more versatile way to go though.


But, when using the ham radio parts, you get BPFs, LPFs, PA & TX/RX switching. On the 7857D, I give it separate TX/RX lines from the Lime, Arduino controls shift registers on the board to do all bandswitching/LPF switching/PA switching & TX/RX with 4 wires coming from the Arduino.
Start asking locals for junker rigs. Look up the service manuals & I am more than willing to help control whatever you get. Some use BCD /shift registers & other ways to control. All pretty easy to run with an Arduino.


Yeah understood, but I have switching and BPF already working … just need to work out some LPF.

I will look more into Arduino.

Keep us posted on your progress, I’m very interested to see what others are doing with their setups.

thx, 73s.

For LPFs, the Kenwood TS-440 (And other Kwoods of the era) have a separate LPF board that has the relays & all. It’s a package that is ready to deploy.


ok thx will keep an eye out for one.

I’m looking at this too

The advantage being that it can go after my 300W PA.

No problem. I was going the TS-440 BPF/LPF/PA, but after adding more junk for VHF/UHF, my enclosure would not work.
Then, I stumbled on the 857 chassis with burnt driver for $125. Makes it a nice package.
So, what software is your preference, or are you going to roll your own?

Re software - whatever works (with TX support) ! I have tried yt7pwr’s SDR software and it looks good but its not working for me. So I guess SDR Angel is the other option ? Any other recommendations ?

Here is my setup with the mini PC (i5 CPU) and the location it will be remotely located at. I had the remote setup with a Flex 2000 about 10 years ago, but PC’s ran hotter back then and used much more power so it was only used for a few months and I pulled it down … sold the Flex.

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SDR-Console is getting Beta tested shortly, with TX for the Lime.


You may want to look at the Udoo X86 ultra & the forthcoming Udoo Bolt. Both good PCs low power consumption. The X86 Ultra is better than the 4 year old laptop I am on. The Bolt will be 4X faster than that.


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@yagigain - Stephen,

Right now, the best app for real HF work is SDRAngel. I have had it successfully running on several platforms (Windows with LattePanda, Ubuntu 18.10 with UDOO Advanced card) and both platforms operate on HF/VHF/UHF/SHF without any issues at all. The interface is a little challenging at first, but once you get the hang of it it runs pretty well on all the frequencies and modes that the LimeSDR can tune.

We are ALL certainly waiting for SDRConsole to appear so we can try it on the LimeSDR. The interface for that is more intuitive and has been the ‘gold standard’ for a lot of SDRs (SDRPlay, BladeRF, HackRF, etc). Having it function with the LimeSDR has been a wish list item for A LOT of us over the past two years since the LimeSDR went mainstream. Once it’s released, the ham community really owes @SimonG4ELI a debt of gratitude as well as some well earned greenbacks for his current effort to provide transmit for the LimeSDR.

Your effort looks great and I, too, will soon be in the mix bringing my spin of a multiband Amateur Radio transceiver using the LimeSDR into view…Stay tuned for that…

73 de Marty, KN0CK

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Hi Marty,

Yeah I tried (battled !) SDR Angel a few months back. I tried it again last night … a couple of nurofen later and I have gone back to good old HDSDR ! I just don’t find SDR Angel at all intuitive … granted I could probably get use to it. I ended up getting it running and could see signals but it just would not output audio to my virtual sound cable or even the standard sound card (everything else does). So in the end I reinstalled the Lime Drivers and went back to HDSDR … I’ve been using HDSDR for many years for several different SDR’s and I love it, even if it is on the simplistic side. It would be great if they could incorporate tx support (I hear its on the cards).

For now I am rx only and have some HF signals tickling the LimeSDR. I do see some “birdie” type signals regular intervals though. Perhaps its from the USB port or the close by PC.

Anyway looking forward to hearing a few LimeSDR’s on the bands … perhaps we could start a LimeSDR net someday !


I have some good news. The Lime is more sensitive than my FT 757 … and the FT 757 was more sensitive than my Flex 2000 (that’s one reason I sold the Flex). So the Lime is performing very well.
My antenna is just an offset dipole hanging over the house so there is S7 noise. In these conditions at least the Lime wins.

Next I’ll set it all up on the hill. I’m really happy about the sensitivity because what’s the point if the thing is half deaf. It is being fed with an LNA … but the FT 757 has an inbuilt LNA too and that was turned on.



Further testing for a couple more days on RX… I added my SDRPlay RSP2 into the mix.

The RSP2 is a very sensitive receiver. The Lime was as good and in some cases better than the RSP2. On 80m the Lime was better than the RSP2, on 20m they are about equal. Both the Lime and RSP2 are significantly more sensitive than my well looked after and maintained FT 757.