Output gain control in digimode working - hints

When running digimodes, the controlling of the RF output in older or "simpler" transceivers can be a little bit tricky. The reason is that the AF gain is adjusted according to human voice and thus it depends on where on the waterfall spectrum you are sending. You might have noticed that the gain is smaller at the edges of the waterfall.

Output power as function of frequency. In this example HRD DigitalMaster and my IC-718.

Previously I wrote how this issue is handled with Ham Radio Deluxe's DigitalMaster: using the centering button and filters. This helps also greatly in QRM/AGC issues.

In JT65 working I mostly want to see the full spectrum, and in JT65 software there is typically no centering button. In the HB9HQX edition of JT65-HF this is solved neatly with a gain control window:

The audio gain control window in JT65-HF HB9HQX Edition

The gain control window above is not needed, when I work with my TS-850S, because there is a handy mic gain knob at the front of the rig. However, there are no such handy knobs in simpler transceivers, like my IC-718, so the gain control window is crucial for convenient working.

Australia on 80m band with 25W and delta loop antenna

My first contact to Australia on 80m was made tonight. Wow! (my feeling :) ) The mode was JT-65 and power 25W. The antenna was my Inverted Delta Loop for 80m.

I was very weak to VK4CMV Julian, and I had to repeat my info to him, but finally the QSO was finalized.

I have been playing with this vertical delta loop antenna on the 80m band, and I am now convinced that it is especially good in listening. I have hard time getting heard by DX stations when I work 25W (digimodes) and 100W (CW), but I have found out that I almost always hear distant stations that are spotted on the dx cluster. I have worked some U.S. stations before on the 80 meter band (mostly CW), but DX is rare stuff for me on that band.

UPDATE 28. Jan 2014: mail conversation with VK4CMV Julian:

Quoting a mail conversation with VK4CMV after permission from him:

Nice blog page Sauli - great to work you on 80m.
JT65a has opened up the possibility of QSOs on 80m and 160m which were previously very difficult.
73 Julian

PS: Have a look at what I was copying on 18th December (attached) - this should encourage people to try 80m JT65a!!

Julian continues:

Sauli - just in case people think they need a high quality rig like the K3 for JT65a - take a look at this video comparison I did between the K3 and Ft450d ...

http://www.youtube.com/watch?v=PgIaAz94oVo

JT65-HF HB9HQX Edition

I occasionally play with JT65 on HF. JT65-HF has been the best application so far. Recently I found an improved version of it (luckily it is open source so anyone can improve the program): JT65-HF HB9HQX Edition.

It has many clever new features. The picture above shows the most important improvement: Statistics and improved station information. This software can be downloaded from here.

New digimode: SIM31!

A new digimode was announced and I found it immediately interesting. Very efficient coding and as an option: automatic PSK QSOs! Here is the SIM31 homepage. For some reason it feels like magic, when I see me doing a full QSO by just looking at the rig and the screen :)

My first SIM31 QSO.

SSTV tried

Because of bad condx I decided to try something new instead of DX working: I tried SSTV (Slow Scan Television) with my HRD DigitalMaster. After a while of playing I got my first SSTV QSO on 14.230 MHz.

14.230 MHz, 25W, Delta loop 20m up

I tried also the MMSSTV software, but since I am so used to DigitalMaster, I think I will stick to it.

EU PSK DX Contest 2013

After a long break I took part in a digimode contes las weekendt: EU PSK DX Contest 2013. I competed in the 12-hour class. Claimed results:

Using filters in HRD DigitalMaster

I have moved this article to my new site, please click here to find it.

160m band with short vertical

This week I conquered the 160m band with my 10m high copper pipe vertical. For some reason it tuned well with the automatic tuner in my TS-850....maybe because of losses in the 50m long RG50 cable? I was surprised: I managed to get QSOs on both CW (100W) and JT65 (40W). It was not easy, so now I know what my next antenna project is: a decent DX-ready antenna for 160m. Hopefully very soon!

Reverse Beacons hearing my CW signals

pskreporter.info reporting my 160m activity  Mostly JT65 and obviously also one CW skimmer.

An almost ordinary night on 20m: JT65 DX thrill

The sunspot number is 73...the K index is 1. Looks like an ordinary august night. I'll show you how it looks like with the JT65 mode. I am using the JT65-HF program here, with my TS-850S using 40w to vertical inverted delta loop. (Here is my station info).

Australia  and others contacted at about 22PM GMT...and many others heard me, as seen below 

pskreporter.info: These stations heard me calling CQ. Zooming on US below

US zoomed in the map above.

I had a few nice DX contacts tonight with this mode. Yes, a lot more stations than I can image with SSB. Yes, CW competes (almost) with this, and sometimes also that is funny. Yes, I agree, there is not very much information exchanged in JT65 QSO, but quite real signal strength reports (S/N in dB) anyway! You may agree, that it's not very common in CW and SSB...59 right? ;)

HRD as QRM source...what?!

This morning I was listening on the 15m band with JT65-HF. Obviously some Japanese stations there. In parellel with JT65-HF i started Ham Radio Deluxe and soon I heard a noticeable difference in the white noise level.

The waterfall picture shows the noise level difference with our without Ham Radio Deluxe main window.

What?! Did HRD cause that? I closed the HRD main window and the noise disappeared. And restarted, and it came back. The picture above shows the difference in noise levels.

The first thing I found out was that when HRD-rig connection is cut off, the QRM stops. So, obviously the HRD software isn't the problem after all? :) Then it occurred to me: maybe the TS-850S USB interface could be the cause?

Later I found the solution: I moved the PC interface half a meter away from the rig and the noise disappeared!

Don't always depend on AGC in digimode working!

The effects of receiver gain, dynamics and AGC (Automatic Gain Control) are quite easy to "measure" with digimode waterfall displays.

I suspected that the AGC of my Kenwood TS-850S is not very optimal for digimode working, so I arranged a simple AGC test. The frequency was 14.076 (the JT65 section on the 20m band) and the antenna was a 20m delta loop up about 20m. The JT65 mode was chosen, because the transmission times are long enough to get accurate comparison results.  During the JT65 transmission minute (less...47 seconds?) I switched the AGC on and off a couple of times, after having adjusted the RF gain manually to an acceptable level. 

Here is how AGC affects reception of JT65 signals. Click the image to show it bigger.

The figure above shows interesting things:

• When AGC is On, the RF gain is automatically reduced so that the strong signals don't cause clutter on the band. However, some weak signals become unreadable. Since this TS-850S has quite good receiver dynamics, it is not very critical, compared to cheaper rigs, but anyway: some weak, possible dx stations suffer besides strong signals.
• When AGC is Off, the gain has to be adjusted manually with the RF gain knob. If gain is 100% without AGC, the strong signals clutter the band and probably make signals unreadable. When finding a level where there is a little bit background noise, there could be still some clutter, but weak signals get readable. In the figure above there is some clutter, but it does not affect the readability.

When I found out this for the first time, it felt like magic: I can find new stations by tuning the RF gain manually! And more stations with less gain...weird, eh? :) Not quite so, but the best compromise has to be found. The RF gain knob is now of the most important knobs on my rig in digimode working. Soon I worked new continents and countries on all bands. Optimally the AGC should to be tuned all the time, depending on the situation on the digimode band. 

Don't forget to set the AGC on and the RF gain to max when working CW and SSB! I have missed some opportunities because of my bad memory here... The default AGC level is most probably still ok for CW and SSB working, but e.g. this rig was created before modern digimodes did exist! In modern rigs there are often separate settings for digimode working and I suspect the AGC is also affected.

Note that simpler rigs, like my IC-718 do not have any possibility to switch off the AGC and set the RF gain manually.

Last note: Don't mix AGC with ALC (Automatic Level Control). Also ALC  is important in digimode working, at least in phase shift keying modes, but that's another story.

My EPC Ranking by 05/2012

I checked my status on EPC Award Ranking List. Obviously I'm ranked 192 in the world, and 4th in Finland:

This is obviously because of my active first year 2011....after my 22 year pause :)

Internet does not kill this hobby!

I now and then here arguing about internet killing this hobby. I have always seen it the other way around: internet adds new dimensions to the radio amateur hobby. Many of my blog texts explain my view already, but here is once again an example:

I just I inspected PskReporter.info after a JT65 session with JT65-HF on 21.076MHz. I found that these station in the States heard my signals:

Well...that was interesting info to me, in many respects:

1. Good propagation to US! All those are potential QSO friends, giving me an opportunity to work new states for my WAS award. After checking the PskReporter info many days in a row, I can now conclude that there are often quite good propagation conditions from my QTH to US on 15m in the late afternoon, even when the general conditions are quite poor. Also the west coast, just before the band closes for the day.
2. My 5/8 vertical and 50W is enough for DX working
3. Last but not least: it feels good to know that my signal (with the power of a light bulb) propagates so easily so far! :)

How this works: JT65-HF and other digimode software upload decoded stations automatically to PskReporter. The same works e.g. with HRD DigitalMaster-780 (when using its SuperBrowser you can let your computer upload decoded stations to the pskreporter database; for you and fellow hams to analyse).

My TS-850 digimode stuff :)

This mess looks almost fun: This is is what I need in order to work digital modes with my TS-850:

Wires, USB-serial interface, rig control, PTT, audio cables, audio transformator...messy? :)

In more modern rigs there is just one USB cable and that's it. But my setup looks more nerdish, doesn't it?

Comparing an internal soundcard with Roland UA-1EX

I got the opportunity the borrow a "hi-fi" USB soundcard from my local club OH2AAB. I made a brief comparison with my internal laptop soundcard, using DigitalMaster 780 and my rig TS-850S on 7035kHz at about 9PM GMT.

The PSK screen using the internal soundcard of a HP Pavilion dv7; strongish laptop

The PSK screen using the Roland UA-1EX soundcard

I was a little bit surprised: I don't see very much difference. Or am I blind?  A more thorough test would maybe  reveal the differences...I don't know. Let's see if I have time to do that. Also on the transmit side. Also I could test an ancient PC...to get some baseline for comparison. My  current laptop is quite an efficient multimedia laptop.

US west coast open on 21MHz in the afternoons

There are nowadays good conditions to the States on 21 MHz almost every late afternoon.

Map from pskreporter.info at about 4pm GMT 19.2.2012

Good opportunity to work US states...especially the west coast is coming strong. The west coast is normally a lot bigger challenge than the east coast.

I nowadays work US also on 7MHz in the early mornings. The same 10m vertical antenna is used for both 21MHz and 7MHz. It is up 12m and with three 10m radials. For 21MHz the antenna works as a 5/8 wave gp, which has a low lobe; good for dx working.

ARR PSK63 Contest results

My first digimode contest resulted in a 10th place: http://www.ct1arr.org/pdf/Class_psk63.pdf

Little pistol goal: continent-shooting afternoon :)

I had a few hours for my radio hobby (again). I found that there were good conditions on 15m, so I chose to set a personal goal: trying to get QSO with as many continents as possible this afternoon. The result: 5 continents in 3 hours. As the log shows, I tried for over an hour to get africa in the vanishing conditions...finally succeeded also there, yes!

Yes, the mode was PSK31. Normally the best chances to get many dx contacts is with PSK. I like CW also, but PSK is obviously more popular nowadays, so it made it my choice in this brave quest :) SSB is also fun, but considerably trickier to get DX QSOs with 50-100 watts and dipole antenna.

Doubling digimode output power with a fan

In CW and SSB transmitting a typical 100W transmitter deals easily with the power set to full, because there are always the pauses between the peaks in those transmitting modes. In contrary, most digimodes send for long times without pausing; full duty. The transmitters aren't built for handling full power for longer times: the heating becomes the big problem. The commonly used way to deal with it is to half the transmitter power to 30-50W. That is OK for normal e.g. PSK QSOs. In some big RTTY pileups I started to long for the full 100W, so I took a 12V computer fan, and installed it like this:

The fan is blowing towards the hot part of the transciever.

The 12V power is easily got from the transceiver DX source.

I tried this installation in a few long digimode sessions, using the full power. The transmitter remained cool, so this seems to work. I gained 3dB, a half S unit. Sometimes it may make a difference! Can you get a 3dB gain cheaper than this?

New digimode tested: Feld Hell

Poor DX conditions made me try something new: found a Feld Hell CQ and answered.

My first Feld Hell QSO

Feld Hell is a Hellschreiber mode, which is in fact a much older communication mode than the PSK  modes. As with morse/CW, the communication is meant to be interpreted by humans instead of computers. When CW (at least originally, and still best) relies on human ears, Hellscreiber relies on eyes! Read more e.g. here.