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Using a Remote SDR On Older Rigs

from Greg Danes, KJ4DGE on February 8, 2019
View comments about this article!

Using a Remote SDR On Older Rigs
By KJ4DGE

As most followers of Ham Tech have surmised looking at the current crop of new radios for HF from Yaesu, Kenwood and Icom, they have incorporated SDR into these new radios as it’s a natural progression for ham users today. Many of us however do not have the thousands of dollars to buy these radios and even though we may have a fairly recent solid state digital radio, it does not have the ability to “see” signals adjacent to the one we talk on in real time.

Many hams today have a computer they use for DX spotting and looking up a fellow ham’s call sign on QRZ. You can now use the many remote sites that have been setup for hobbyists to listen and “see” these signals online.

One of the more popular sites is https://sdr.hu/. This site lists literally hundreds of remote SDR sites you can listen to and see the signals across a wide range of the amateur radio spectrum. By taking either your cell phone or tablet and this site you can add a cheap SDR component to your radio. These signals are real time but have a delay of course of a few seconds due to things like your router download speed and the internet. The picture below shows the 80/75 meter band this morning via a remote SDR run by K2SDR in NJ/ USA. Many others are spread out across the US in towns near your QTH. It makes little sense to use one in Greece for example if you want monitor signals near you.

The uses of these remote sites are limited to usually a number of users (4), on a first on first served basis. The low number has more to do with the software being use (Kiwi-sdr) than the remote hardware but that also is a factor. By using the site as a receiver for your rig, you can see adjacent signals over a wide spectrum of the band and also hear who is there. It can also be used to see YOUR signal and how much bandwidth and purity you are putting out on the band as well.

The nice part of all this is the hardware is already there. You do not need a SDR receiver or an antenna. Given the cheap cost of these nowadays, yes you could use one of your own but it would likely be overloaded by your transmitter is not totally fried!

The only thing you really need is to have internet access and a cell phone or tablet. I use a cheap 8 inch Visual Land tablet and the website to spot signals that may fade in and out at my QTH but come in strong at the remote site to see if I can work the same station. Many times I cannot even hear the signal in VA the receiver is picking up in NJ or NC but its there and if propagation changes in my favor I already know who and where the incoming signal belongs to.

Here are signals this morning on 3.860. Notice the wider the vertical band the stronger the signal. You can use this to find weak stations that may be DX stations or are farther away from your QTH.

Bear in mind that most cell phones and tablets are notoriously bad audio-wise so to hear the signal better you may need a set of ear buds. But the point is seeing where these signals are so you can tune to them quickly. And no, the software will not give you call signs popping up on the screen. Still this simple addition to your toolbox will allow those with older gear a leg up on finding perhaps that rare DX on the bands you have been looking for.

The KIWI-SDR running on these remotes let you change the mode from CW, USB, LSB and FM and tailor the signal all on the remote receiver. What makes this all possible is a SDR/software combo for the internet. To learn more about this go to http://kiwisdr.com/.

These are generally not cheap 20 dollar SDR-dongles but dedicated SDR receivers that combined with the software open up a new world of online HF listening.

Below is the Kiwi-SDR module. I personally don’t see me having one of these in the near future, but who knows what type of SDR radio or transceiver is right around the corner?

The purpose of this article is to show the experienced operator and the novice one more tool to use in the ham arsenal for DX and having a fun learning experience.

The purpose of this article is to show the experienced operator and the novice one more tool to use in the ham arsenal for DX and having a fun learning experience.

Software defined radio is here to stay and many op’s today use Flex-Radio type transceivers. I like the older style big rigs with lots of controls and dials but that’s me. Someday when I can afford a Flex or other state of the art rig that may change but for those wishing to learn more about SDR, try this and see if you might find it useful.

Hope to hear you on the bands.

73
Greg/KJ4DGE

Member Comments:
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Using a Remote SDR On Older Rigs Reply
by WB8LBZ on February 8, 2019 Mail this to a friend!
I have been using SDRs since the early Flex1K and 3K. I also have an Anan800DLE as my Daily Driver HF rig. I have made use of the KiwiSDR system for monitoring HF Traffic nets when I can't hear the NCS. I have an assortment of USB connected SDR devices. I'm ALL in for SDRs. I still have a few traditional radios for those times when I need the basics for a local net or Field Day (most of the guys in the club are afraid of SDRs).

73, Larry WB8LBZ
El Paso, TX
 
Using a Remote SDR On Older Rigs Reply
by KB5UZB on February 8, 2019 Mail this to a friend!
I hadn't run across https://sdr.hu ... I used http://websdr.org extensively as background noise at work. It's fun to listen in on Rag chews in the UK and Europe. sdr.hu should be more handy for me for signal monitoring though. It looks like there is a receiver closer to me that has a better noise floor than the one on websdr.org.
 
Using a Remote SDR On Older Rigs Reply
by KB4MB on February 8, 2019 Mail this to a friend!
Why not add a $20 dongle and a T/R switch and have a local SDR to use as a receiver or panadapter? That way you can hear exactly what your antenna picks up? Even the RTL-SDR can receive without a downconvertor now.
 
Using a Remote SDR On Older Rigs Reply
by K6OFG on February 9, 2019 Mail this to a friend!
I regularly use an SDR receive station to hear stations that I communicate with. We all tune into the SDR station which hears our signals. My computer becomes my receiver.
Our nets would not be able to continue without these stations.
Steve.
 
Using a Remote SDR On Older Rigs Reply
by N6JSX on February 9, 2019 Mail this to a friend!
SDR's are interesting but I see a few problems not often discussed.

Like SDR's used in/near high RF environments (city dwellers); I do not see RFI rejection keeping the SDR from suffering RF swapping/saturation?

The kiwisdr in the article is not $20 but $249 from Amazon.

The big issue, I see, in using an SDR in an active HAM Shack is antenna switching/TR-protection. How-to SHARE the same antenna with the 100W HAM radio and keep the 100W TX out of the SDR.

No one addresses these common issues or how-to protect the SDR's from 10mW-100W TX in close proximity or on the same coax/antenna line. Just throwing a manual antenna switch will likely not be enough to protect a sensitive SDR front end.

Answer these issues and the SDR can become a fun tool.
 
RE: Using a Remote SDR On Older Rigs Reply
by KB4MB on February 9, 2019 Mail this to a friend!
The RTL-SDR is $20 on Amazon. I have one. I also have the MFJ-1708 SDR T/R switch. It grounds the SDR when you transmit (it has a grounding RCA plug that you hook up to your transceiver from the PTT line). Been operating for awhile now, full 100w with no issue. I am also using an "older" Icom 718. Using hamlib, the SDR software I am using tracks where my rig is, and also when I click on the screen on the SDR, my rig follows. I can choose NOT to do that if I wish. I can also choose to either listen to the rig audio or the SDR audio. I do both - sometimes I prefer using the rig since there is no audio delay, sometimes I prefer the SDR because I can narrow the bandwidth. There are several videos on YT with this setup.
 
RE: Using a Remote SDR On Older Rigs Reply
by KB4MB on February 9, 2019 Mail this to a friend!
Here is a video that shows that setup:
https://youtu.be/k-jOFwSBZLs

 
RE: Using a Remote SDR On Older Rigs Reply
by KJ4DGE on February 9, 2019 Mail this to a friend!
A 20 dollar dongle would work, But you have to more or less dedicate a PC to it.
 
RE: Using a Remote SDR On Older Rigs Reply
by KJ4DGE on February 10, 2019 Mail this to a friend!
Since the KIWI sites are already there you just look at you Iphone, Android or Ipad while using your rig at the same time. No hardware investment and you can even find sites North and South, east and west and compare Propagation on the same frequency. Nice way to check nets as well to see who is hearing who.
 
RE: Using a Remote SDR On Older Rigs Reply
by K9MHZ on February 10, 2019 Mail this to a friend!
“No one addresses these common issues or how-to protect the SDR's from 10mW-100W TX in close proximity or on the same coax/antenna line. Just throwing a manual antenna switch will likely not be enough to protect a sensitive SDR front end. Answer these issues and the SDR can become a fun tool.”


That has never been an issue in the microwave world, and very high performing switching devices are easily used in t/r switching between system components. This wouldn’t be challenging at all.


 
RE: Using a Remote SDR On Older Rigs Reply
by K6AER on February 10, 2019 Mail this to a friend!
I use a SDR in the shack for band screen display and have found not only disconnecting from the antenna on transmit is necessary but actually putting a short across the input to the SDR receiver is needed to prevent front end damage. Still my own transmitter is displayed at maximum amplitude on the screen.

Much of the displayed amplitude is from the antenna radiating directly to the semi shielded SDR receiver. Spending a little more for a shielded case will save you a lot of trouble during application.
 
Using a Remote SDR On Older Rigs Reply
by BURGERLOVER65 on February 11, 2019 Mail this to a friend!
Most of the kiwisdr sites are set up so you are unable to enter wanted frequencies. Up until now it seems only the administrator can do so. So much for kiwisdr use.
 
RE: Using a Remote SDR On Older Rigs Reply
by KJ4DGE on February 11, 2019 Mail this to a friend!
"Most of the kiwisdr sites are set up so you are unable to enter wanted frequencies. Up until now it seems only the administrator can do so. So much for kiwisdr use."


Not true, and besides why type when you can click on a line on the screen and use up down arrows to fine tune?

Check how many users are already on. If its 4 you can listen and such just not control the radio remotely.

 
RE: Using a Remote SDR On Older Rigs Reply
by BURGERLOVER65 on February 11, 2019 Mail this to a friend!
It's possible my cell phone and kiwisdr don't work well together. For one thing the interface takes up about 90 percent of the screen. All I can do is choose band then use plus or minus buttons.
 
RE: Using a Remote SDR On Older Rigs Reply
by BURGERLOVER65 on February 11, 2019 Mail this to a friend!
I would be really embarrassed to hook my wagon to operations like sdr.hu and kiwisdr.
 
RE: Using a Remote SDR On Older Rigs Reply
by N3HKN on February 11, 2019 Mail this to a friend!
Skip KIWI - do it yourself. I run an Icom-7300 in this mode. The switchbox protects the "delicate" SDR (7300). I can then use either the 7300 normally. Or, use the RSP1A SDR receiver with the 7300 transmitter.

I can see NO MATERIAL DIFFERENCE, on receive, between the RSP1 SDR and the 7300 on receive. This is using HDSDR or SDRuno (comes with the RSP1A) and the 7300. Point and click on what the RSP1 receives to tune 7300. The PC is NOT dedicated. I can do the hamming while watching CNN on the same screen.

I did this because I have high noise. So, I bought the W6LVP reeive only amplified loop with its switchbox. Loop is amazing. Switchbox flawless. Choice of two darn good SDR receivers.

I need an amplifier because of condo attic dipole on transmit. Will use the money to buy an Ameritron 811 amp.And, an "older" used-low-cost radio for a transmitter.

Of course if you are trapped in a no radio/antenna at all setting then Kiwi is a way to go. May need association with a local club to transmit.
 
Using a Remote SDR On Older Rigs Reply
by ON4AA on February 13, 2019 Mail this to a friend!
400 or more simultaneous users all on different frequencies are not an issue for some of the larger http://websdr.org/ remote receiving stations.
Granted, these are not using KiwiSDR.
 
RE: Using a Remote SDR On Older Rigs Reply
by ON4AA on February 14, 2019 Mail this to a friend!
I almost forgot. Here is my recipe to retrofit a 1992 Yaesu FT-990 with an SDR tap:
https://hamwaves.com/sdr/en/index.html
 
RE: Using a Remote SDR On Older Rigs Reply
by N3HKN on February 14, 2019 Mail this to a friend!
I did a similar thing with a Kenwood 520 (hybrid tube rig). I grabbed the RF from the 3.8mhz IF and fed it to a Softrock SDR. I had better reception/selections AND a panadaptor on a 520 rig. Today I have no reason to open a rig to gain either better reception or a panadaptor. Simply tap into the receive signal from the antenna. You can use a splitter for electronic formality, or simply mechanically/electrically tap the into the the antenna with an SDR. Making and breaking the tap to the SDRPLAY RSP1A showed no discernible degradation of reception by the Icom 7300. Do not forget the antenna switchbox to xmit directly into the antenna and switch to the receive port (SDR) when the transmitter (PTT signal) is off.

The ideal is to find a cheap top level superhet rig that can't receive but can be computer controlled. Software on a PC (no programming) and a $120 SDR and you have a fully functioning receiver that you bought for peanuts.If you have issues with the RSP1A, say from strong signals, there might be better unit for that issue. I wish I had strong signals in my condo.
 
Using a Remote SDR On Older Rigs Reply
by W2FBS on February 14, 2019 Mail this to a friend!
Hi Greg,

Great article. A lot of the guys on the 3838 Breakfast club use remote SDR's during the net. I use it them a lot as net control when the band is long or otherwise not cooperating.

I will forward this article to some of the guys who have asked about remote sdr receivers.

Hope you are doing well.

73, Rich
 
RE: Using a Remote SDR On Older Rigs Reply
by KJ4DGE on February 15, 2019 Mail this to a friend!
ON4AA
Thanks for the link, really nice.
 
RE: Using a Remote SDR On Older Rigs Reply
by KJ4DGE on February 15, 2019 Mail this to a friend!
W2FBS

Hi Rich!

Will try to make the net more often been busy getting into semi retirement mode so to speak. Now if I can just find a part time JOB as a vet assistant life will be very good :)

73

Greg
 
Using a Remote SDR On Older Rigs Reply
by WD5ACP on February 23, 2019 Mail this to a friend!
I recently added the very low cost (~$20) RTL-SDR USB dongle + the free AirSpy software to add a 2nd receiver for use with my Drake TR-7. The Drake has RCA Receive IN and OUT jacks on the back. I just replaced the small jumper that was between them with an audio Y adapter (two males, one female)! Then I tack-soldered an single RCA male audio cable across the SDR's SMC antenna jack (since I didn't want to mess with stiff coax cable and adapters) and keep it plugged into the Y adapter. It works GREAT as long as you have an antenna tuner (I keep an MFJ Diff-T tuner inline with the Drake for antenna switching and keeping the SWR low anyway) - Without the tuner the low cost SDR is absolutely trashed by the local 50KW AM broadcasts stations, but with the tuner in line, the HF bands receive is ALMOST as good as the Drake!

The beauty of the Drake is the rec in/out loop is downstream of the Drakes' mechanical band filter and works even if the TR-7 is powered off! No TX/RX relay needed as the loop is only on the REC antenna circuit.
- I can watch the entire band on the laptop, listening to QSOs, etc, then just dial in what I want with the Drake. Great combination!
 
RE: Using a Remote SDR On Older Rigs Reply
by G8JNJ on February 25, 2019 Mail this to a friend!
Check out CATSync

It allows you to tune web sdr's to and from rig CAT (and other) commands so that both are sychronised.

It will also allow web sdr's to be tuned with CAT commands from software such as JT and WSPR modes using an Elecraft rig emulation.

Regards,

Martin - G8JNJ
 
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