ALT-512 Transceiver now on Sherwoods Tables

I’m certainly no expert on interpreting the receiver test data from Sherwood Engineering, but for what it’s worth, the new ALT-512 radio has been added; 8 places above the KX2:

It is one of the highest ranking portable transceivers on the table, well ahead of many very expensive main station rigs. Is anyone using this rig?

A short review (or even a long one) would be nice :wink:.
73 de OE6FEG

Hi Matt,

I don’t have that rig but I own the previous model LD-5.
I wrote a review here:

I guess it will be similar, but perhaps with some changes in the hardware…
If anybody wants to send me one part I will be glad to repeat the test :wink::innocent:

73 de Ignacio

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Nothing against the new ALT-512 SDR, but the average SOTA operator (like me) appreciates the integrated ATU and low RX power consumption of the KX2.

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You’re absolutely right Heinz, I use the KX2 myself and have no intention of swapping. However, I think this new radio is a strong contender that newcomers will definitely want to consider when deciding what rig to buy. With a built in soundcard, it may well have the edge for those intending to use mostly data modes. Yes, current consumption is not the best out there, but it’s better than some.
73 de OE6FEG

I posted here a while back on this radio. Looks interesting. I might just pick one up. At the time, the only op info I could find was from Rick, DJ0IP, here:

73, Todd KH2TJ

I see now that Rick’s post and this one here are on the Aerial-51’s webpage:

Still not much operator info out there - I think they just became available in May. I like that it’s plug and play with digital modes, running with the laptop, etc etc…

Bear in mind that scoring highly on the Sherwood Engineering table tells you very little about how suitable a radio is for portable operating. That’s down to a whole host of factors - some of which will depend on user preferences.

Just downloaded the manual for ALT-512. On paper it looks like it suits my SOTA use better then the KX2 that I have used for the last 40 activations. Difference in weight and reciever power use is not significant. I do use resonant antennas so tuner is not needed. My activations use SSB when propagation is ok, but much of the time I have to fall back on FT8. ALT-512 is ready for both out of the box, for the KX2 one needs to buy a microphone and sound cables, and some isolation device to connect to computer for digimodes. The waterfall display and additional bands are bonus. The Sherwood results are an indication of the quality of the reiciver, even though the narrowband dynamic range is propably not limiting when using SSB or WSTJ-X (FT8) in SOTA.


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Transceiver characteristics ranked on their importance based on how I use the radio:


  1. performance
  2. user interface
  3. everything else

SOTA & portable:

  1. weight
  2. size
  3. ability to monitor running parameters (battery level, SWR)
  4. ruggedness & ingress protection
  5. reasonable output power (ideally ~20W)
  6. internal battery
  7. internal tuner
  8. ease of use
  9. internal digimode interface
  10. efficiency
  11. ability to pass through airport checks without raising suspicion
  12. performance

This is an excellent showcase of what SDR technology can do and I expect the IC-705 performance will be in the same ballpark. However, on a modest portable antenna with a few watts of output, receiver performance is far from critical. People are happy even with receivers that use SA602 in the frontend :slight_smile: .


An isolation device is not needed to connect a computer to the KX2. If you have hum and noise problems, fix your the grounding and bonding in your shack. Isolation transformers ignore the problem instead of fixing it.


Are you sure? I have used a lot of QRP rigs /p over the years and even with small portable Antennas very often my QSO got lost in space if another CW station happend to work less than 5 kHz obove my QRG producing 10over 9 at his QRG but was strong enough at my QRG. In /p operation I love RX having high dynamic range, performance definitively is critical for me.
Yes, I am also happy with my NE602 based RX if they are properly designed. Using good preselection and low frontend gain can make an NE602 RX a performer :slight_smile:
The ALT-512 is an excellent alternative at moderate price.
73/2 de Peter, DL2FI

It’s worth pointing out that the rigs like the KX1 and FT817/818 appear nowhere on Sherwoods tables. However, the LD-5 and LD-11 from LNR precision have a similar form factor:

They both seemed to be well received by the /P SOTA community: G0POT did a nice series of videos on YouTube about the LD-11:

They have low-ish current drain as well, which is also seems to be becoming an important benchmark for many operators. If the receiver is also top class, well that’s a nice bonus. What would be really nice, as I said in my original post, is if someone could review it for us.

             73 de OE6FEG

I have an LD-11 on loan. I tried the rig a couple of weeks ago but I didn’t like the keyer. I’ve had comments passed to me from others about the poor CW implementation also.

I did the firmware update to the latest (final) version to see if things would improve, but there wasn’t any improvement.

At the end of the day, if the LD11 and LD5 were superb, well polished radios, they’d still be in production.

I want to like the little radio but so far my 18+ year old FT817 beats it by a margin.