IM improvements using DPD with a SSPA

The question that a lot of users seem to have on their mind is "What benefits, if any do I get by using ICOMS DPD in conjunction with a Solid State Power Amplifier (SSPA)"

Well, I measured a 6dB improvement. 

Measurement setup:

• SPECAN: SDR-IQ
• TAP: VK5HW (50dB)
• ATT: 20dB
• PWR: 1000W
• ANT: Dummy Load (VSWR 1.08:1)
• Software: SpectraVue V.3.44 Beta 0

DPD off

Two tone test:

Result:

1st Value    -31.311dB

2nd Value    -31.455dB

3rd Value    -52.398dB

4th Value    -53.545dB

IM Max     -22.2dB

IM Avg     -21.6dB

NOTE: 1st and 2nd are the two tones and 3rd and 4th are IM3.

Look at IM3 and IM5, they are nearly the same in strength.

And the below using my Voice Caller calling CQ:

Result:

1st Value    -23.996dB

2nd Value    -31.168dB

3rd Value    -49.526dB

4th Value    -53.689dB

IM Max    -29.7dB

IM Avg    -24.0dB

DPD ON

Two tone test:

Result:

1st Value    -31.168dB

2nd Value    -31.311dB

3rd Value    -58.996dB

4th Value    -59.139dB

IM Max    -28.0dB

IM Avg    -27.8dB

Well, we do see about a 6dB improvement on the two tone test which is better than a Mosquito fart. But I believe the below is quite a good example on how well it improves your VOICE signal!

And below, using my Voice Caller calling CQ:

Result:

1st Value    -20.840dB

2nd Value    -27.582dB

3rd Value    -57.750dB

4th Value    -60.143dB

IM Max    -39.3dB

IM Avg    -34.7dB

On average we see an improvement of 7dB again better then a Mossi fart.

So I'd say any improvement, be it only 6dB is an improvement. As such I would recommend to upgrade the IC-7610 firmware and enable DPD however, YMMV ....

Controling the RF-KIT Amplifier via UDP

Having gone through the trials and tribulation of online "shopping for answers" I thought I better write down how I got my amplifier to follow the band/frequency of my radio, an ICOM IC-7610.  

Please note: Many ways lead to Rome, as well to a solution for the amplifier to follow the Radios frequency/band. This is only one of the many.

Since I've already control my radio from my PC via the logging program from DXLAB, it was quite easy to Setup the amplifier to follow the radios frequency/band after some very good information had been passed on from Martinus, CT1IQI.

I first configured the amplifier for network access. I tried using the WiFi Interface but that had intermittent hissifits  so I connected it to my wired network using a STP patch cable (CAT6) and configured the Network interface of the RF2K-S through the menu system.

From the main screen select [MENU] :

and select [Network] [LAN] or [WiFi] :

The default will be DHCP however, I would advise to use a manual IP-Address. It does make it easier in finding the devices IP-address (YMMV). And should the DHCP reservation time out, it might assign a new IP-Address to the amplifier causing future connection issues.

NOTE: If you are using DHCP you'll have to search for the IP-address in your router/dhcp server address table. Make sure to have the address reserved, i.e. map the address as a static address. Consult your manual on how to do so (it would be nice it the amplifier would display its own LAN/WiFi MAC-Address, this would make finding the DHCP assigned IP-address a lot easier)

I've setup my router to act as a Name Server, as such I've also populated the [Name Server] field. (Again YMMV)

To test if the amplifier is reachable from your PC use the ping command. 

hw@rapi4:~ $ ping -c 3 rf2k-s <-- use your amplifiers IP-address (ping 1.2.3.4)

PING rf2k-s (192.168.1.11) 56(84) bytes of data.

64 bytes from rf2k-s (192.168.1.11): icmp_seq=1 ttl=64 time=0.476 ms

64 bytes from rf2k-s (192.168.1.11): icmp_seq=2 ttl=64 time=0.429 ms

64 bytes from rf2k-s (192.168.1.11): icmp_seq=3 ttl=64 time=0.423 ms

--- rf2k-s ping statistics ---

3 packets transmitted, 3 received, 0% packet loss, time 2004ms

rtt min/avg/max/mdev = 0.423/0.442/0.476/0.023 ms

Having finished setting up the Network interface of the amplifier it's time the control Interface.

Select [Interface] and select UDP as the Default operational interface:

Now select [UDP] to select Port 12060 (the default)

and check Listen to active radio.

Now onto the Radio Control Application. In my case that is Commander from the DXLAB suite of applications. 

NOTE: I've been told that Log4OM is capable of the same feat however, I've not tried this.

In Commander open the Configuration Panel and select <Net Serv> from the [General] tab:

which brings us to the UDP Network Service window.

We add our amplifier IP Address and Port number as shown and enable the UDP Network Service. The New transceiver (Xcvr) Delay is set at 10, you might like to experiment here if you are using a WiFi connection.  

That's it for the configuration. For operation you would make sure that you select UDP through the UNIV menu.