Category Archives: Amateur Radio

SOTA activation at South Black Range VK2/ST-006 to complete the MG award

Leaving Canberra at 7am and heading out via Hoskinstown to the South Black Range summit, I was ready by 8:30 am to make contact with a group of SOTA enthusiasts back in Canberra.  The plan was to first use 146.5 fm to make local contacts with whoever was there.  Then go to 1296 MHz ssb to make a few contacts there, and then go to the HF bands.

Right on time, Andrew Vk1AD spotted himself on sotawatch.org showing he was set up and ready for the morning’s contacts with a group of SOTA trainees at Mt Stromlo.

Also Matt VK1MA, Al VK1RX and Ian VK1DI were on other summits.  These four operators were on air on the first day of SOTA in VK1, 1st Feb 2013 and we were all on air when each of us have qualified for the 1000 point Mountain Goat award.

We made our contacts and after the 4th contact, several goat bleats were heard on my radio.

Rock, cairn and Trig at South Black Range
The unique shape of the VK2/ST-006 hilltop. The cairn and trig are on top of a huge rock.

I then moved to 1296 and made contacts with Andrew VK1AD and Bill VK1MCW.  The contact with Bill was made on CW as a first for 1296 SOTA in vk1.

After that it was 80m and 40m.  Conditions were favouring longer distances on 40m and it was necessary to use 80m to make contacts into Sydney or into the Melbourne area or any points closer in.

After spending several hours on the summit and getting colder all the time, it being only just above freezing point, I was suddenly surprised by hearing a voice.  There was Matt VK1MA walking towards me grinning and offering me a Mountain Goat ale.  We are lucky in Australia to have a boutique brewery that has produced this very aptly named ale.

After completing the activation and packing away, Matt helped me carry all the equipment back to the car down the hill a bit, then I headed off to Mt Cowangerong to make it a double activation for the day.

Looking happy having completed the Mountain Goat summit
the operating position at South Black Range. tripod for 1296 antenna at rear.

 

Guyed mast at Cowangerong
Setup at Mt Cowangerong. 2m halfwave on the left attached to a tree, the guyed pole on the right supporting the HF wire antenna.
The doublet wire used for HF contacts at Cowangerong can just be seen here, at the top of the telescopic mast

Two SOTA summits activated for VHF/UHF winter field day

I thought it would be interesting to be within reach of the Sydney and Blue Mountains areas  for this contest.  The Illawarra and Central Tablelands regions are the obvious choices.  I decided to go to Mt Wanganderry, Mt Alexandra and Mt Gibraltar and I optimistically planned to spend about an hour on each, which with travel time would probably consume 6 hours, assuming I was on site for the first summit at the start of the contest at 11 am local time, 0100 UTC.

The bands I could use in my FT817 were 50, 144 and 432 MHz.  Adding a SGLAB transverter I could extend that to 1296 MHz.  Antennas were

  • for 50 MHz, a half wave centre fed vertical in the configuration of a coaxial dipole, with a choke at the half wave point and another a quarter wave lower than the first choke.
  • for 144 and 432 MHz I used a horizontal wire dipole attached to two fibreglass spreaders, mounted onto the fibreglass mast using a hub
  • for 1296 MHz the antenna was a 4 element yagi, with the transverter mounted as close as possible to minimise losses in the RG58 coaxial cable.
    the 6m vertical above the 2m/70cm dipole mounted on the pole

    More detail of the 2m dipole with a CATV BNC/wire terminal adaptor at the feedpoint

I logged my contacts using the VK Port-a-log software on a Lenovo 7 inch tablet computer.  I had the option of trying the latest contest version of this package but the designer Peter VK3ZPF was concerned that the 2 hour repeat contact rule for this contest would not be accepted by the nearest contest option in the contest version.  So I decided to use the standard parks and peaks version of the package.  This worked but required a bit of scrolling up and down to find the gridsquare field when logging the details of each contact made.

The 6m/2m/70cm equipment, an FT817

After reaching the site later than ideal, around 12:30 local time, I set up the antennas and equipment.  To comply with SOTA rules my gear was powered by batteries and the entire station was portable and independent of the car.

The second FT817 was used for 1296 mhz contacts via the transverter
1296 transverter and antenna mounted on the camera tripod

I made some initial contacts on the lower bands followed by some attempted contacts with Tim VK2XAX on 1296 MHz SSB.  I could hear Tim but my 2.5w apparently wasn’t enough for him to hear me.  Then there was a good contact with Mike Vk2FLR close to the Sydney CBD, 96km away.

I was about to close the site and move to the next one when I noticed one of my tyres was flat and I needed to change it before I could move.  After changing the tyre I was able to make repeat contacts with several of the stations I had worked earlier, so I had been there at least 2 hours by that time.  (Not keeping to plan too well.)

But finally by 3:15pm I set off for the next summit, Mt Alexandra, about 20km away.  It is located directly to the north of the residental streets of Mittagong with a parking area at the end of a bush track leading up past the houses.  After packing the bag and hefting the antenna poles, tripod and 2nd FT817, I walked over to the start of the climb up the hill only to find a sign advising that the track was under repair and would not reopen until late July.  So I returned to the car, unpacked it all and set off for Mt Gibraltar, which was now my second and final summit for the day, arriving at about 4pm local time.

Setting up to the east of the first cyclone fenced compound, I was able to replicate my earlier setup fairly quickly and get onto the lower three bands. Connecting up the 1296 transverter and antenna, I found a very strong signal again from the VK2RSY beacon on 1296.420, then made a good contact with Mike VK2FLR albeit at lower signal levels than from the first location.  I don’t know whether I had changed something significant, or there was a connector problem, but signals were not as good as they had been.  There were trees obstructing the view towards Sydney so perhaps they were attenuating signals on 1296.  The distance was slightly shorter than the earlier contact, about 91km.

After uploading my log to the home computer, I found I had made 27 contacts but it is possible one of my contacts was made too early for a valid repeat.

On balance I think this operation confirmed that even a low power radio (5W) can be used effectively from a good location in these events.  I hope others who own similar radios and can make similar (very) simple antennas will be encouraged by these results and participate in future.  I think hearing strong signals on the VHF and higher bands is still fascinating to me and far more interesting than a totally predictable and reliable contact via a repeater.

Restoring memory settings in FT817

After getting my FT817 final stage replaced, and all power settings reset to meet spec, I started to use the radio again and quickly realised that all the memory settings (frequency and mode) had been wiped.

This made it necessary to change bands using the band switch (!) and manually change between SSB and CW mode, or occasionally FM, dialing up and down the band as necessary.  With the frequency settings in memories, I only needed to move between memory channels to go from SSB on 7090 to CW on 7032, for example.  And on higher bands, I had several beacon frequencies stored in some memories, allowing me to quickly move between the various 10m and 6m beacon frequencies to get a quick impression of band conditions.

So today I dug out the details of the FT817 memory manager software, retrieved the file of frequency settings stored on the computer, added a few new ones and saved the lot in the 817.   Then repeated the process for  my second FT817.  So they now have an identical set of frequencies in their memories.  Makes them somewhat interchangeable.

All the second radio is missing is a cw filter.  I have plans to sort that out soon.

The details of the memory manager and how to interface it with the radio from a windows box are all in a previous post to this blog.  I actually read the post to remind myself of how it worked!

The previous post on this topic is here.

The blog documents it all.

 

Sotagoat app on iOS – workaround for “alert” time error

The SOTAGOAT app is a well presented and popular app for iOS and works well on my iPhone 5s and the iPad.

Its features include displays for alerts and spots, just like the sotawatch.org website, configuration options allowing you to choose between UTC and local time for displays and posts, an option to produce a goat bleat when each new spot is received from sotawatch, a filter option to specify which modes you want to be informed about and the time periods in which you want the notifications and bleats to occur. It uses an internal list of summits which can be updated from a sotawatch site and can display a list of summits near to your current location, which it gets from the GPS info in the phone or tablet.

However, the current (2016) version of the app has an error in the time calculations for new alerts. Sotawatch uses UTC dates and times. I have sotagoat set to display and post in UTC.  But the times posted and seen on sotawatch were always incorrect and I observed that they were incorrect by the UTC offset. The app was adding my UTC offset to the UTC times I wanted and then posting the adjusted time to sotawatch.  I have found the error can be worked around by adjusting the alert time as follows.

When posting an alert I subtract my UTC offset from the alert time.

For example to post an alert for 2300 UTC I subtract 11 hours (in DST periods) or 10 hours (in standard time) and post the alert for the adjusted time, namely 1200 UTC.

This is easy for UTC times after 1100 but for earlier times, the date must be adjusted back too. It’s simple arithmetic you can do in your head. For say 0400, subtract 11 hours: I do that by one of these two methods:

  • First subtracting 4 hours to get back to 0000, then subtracting the remaining 7 hours (because 4+7=11) from 2400 to get 1700.
  • Add 24 hours to 0400 (2800) and subtract 11 hours from that (1700).

In each case, because the time is in the previous day, subtract one day from the date too.

What if I was in a time zone that is behind UTC instead of ahead?

I don’t know whether the software error treats both time offsets similarly. It is possible that it is correct for negative offsets.

The error has been notified to the author of the software but as it can take a while for new versions to be released via the iTunes Store, I will use this workaround until it is fixed. The utility of the application is too good in all other ways to stop using it.

SOTA QSO Party 22nd October 2016 at Bobbara hill

My station setup for this event was later than planned.  My original summit was to be VK2/ST-042 and to get access a phone call to the owner of the access road is usually all that’s required.  However after two phone calls getting a voicemail response and no callback, I decided to go to Bobbara Hill, just west of Binalong, although that required a longer walk time as well as an extra 20 minutes of travel time.
Once I left the car, opened and closed the gate and starting to walk along the track leading to the hilltop, I was surprised by the wind strength even on the valley floor.  As I climbed further I found the wind was even stronger on the hilltop.
I started setting up in the eastern side of the hill which happily allowed me to avoid the wind, but when I lifted the antenna pole up into the wind it was being blown around so vigorously in the turbulence that I decided it had no chance of surviving in that position and I moved everything further around to the east side of the mountain.  More delay.
Finally I got on the band and called cq on cw, then worked 12 contacts, many being S2S.  I tuned around for ssb activators but apart from Don M0HCU didn’t hear many.  I did call some but lost out to Europeans.  Looked for Ed DD8LP lower in the band where he was spotted but nothing there.  Twice the pole collapsed mid-contact.  Very difficult especially on a slope and in that wind.
I forgot to spot myself but while the contacts are coming you don’t need more qrm.  I have a 250 hz filter in the 703 but that wasn’t narrow enough to sort through the signals at one stage.  Have to say my sending was affected by the unseasonably cold temperatures, not sure exactly what the temp was, but less than 10C, possibly down to 6C or so by the time I finished.  Others were making mistakes too.
Found the tablet was ok for logging but on cw it is tricky to log an incoming call as it happens.  Pencil and paper are easier for that…
Bobbara Hill looking west
Bobbara Hill looking west
Bobbara Hill SOTA setup
Bobbara Hill SOTA setup
I worked 12 contacts, DL3TU, VK4BJS, HB9FVF, OK2PDT, DL3HXX, DL4CW, HB9DQM, OE5AUL, CT7AGR, HB9AFI, JP3DGT and M1EYP just after sunset. Thanks to all.
The surprise was to finally work Tom M1EYP as my last contact and then I looked up and realised the light was fading fast so I packed up.  Walking back down the hill, I was in near darkness as I approached the car half an hour later.
The next morning I received an email from CT7AGR, Portugal, a very nice message thanking me for the contact.  I was just relieved to make the 12 contacts I did including 8 as Summit to Summit (s2s).
 Update: received another email re the S2S contacts.  S2S are the most desirable of all the sota contacts.

Using the Wifi hotspot from an iphone for the android tablet

I was having some trouble getting reliable linking to provide the android tablet (a Lenovo Tab3/7) with internet access while on hilltops or in parks.

A bit of research found a lot of wave-away-the-problems type of solutions, which didn’t solve it at all.

Finally I discovered a comment about the type of hotspot that the iphone actually provides.  It is not an infrastructure type but an adhoc hotspot.  And more to the point, it does not advertise it continuously.  It only advertises the hotspot for a limited time after being enabled, or after you visit the Personal Hotspot option in the Settings menu.

After some experimentation I now find that the tablet happily links to the iphone every time, provided I go to the Settings > Personal Hotspot item in the iphone and then wait about 10 seconds.  Nothing else needs to be done, provided the wifi password has been set in the tablet.

The other solution I have used from some hilltops is to take a personal hotspot device with me.  As my phone provider uses a provider that does not have as good coverage as Telstra, this provides my tablet with excellent network coverage from places without any service on the other network.

Here’s a pic of the hotspot lashed to a tree on the Boboyan Range summit, 40 km south of Canberra.

 

img_2831s
Telstra hotspot, tree mount variety.

Preventing the “power spike”

This problem was discussed on the moon-net list in May-June 2016.  I thought it was worth documenting what is going on with many radios that produce a “power spike”.

The problem is that the gain of the amplifier chain (from say, final mixer to output) will vary from rig to rig, also the drive level will vary. Therefore the actual gain required of the amplifier chain varies from rig to rig, purely due to component variations and even due to alignment settings, which are probably done fairly quickly at the factory.

The use of ALC to control the gain of the amplifier chain is a typical and common approach taken by manufacturers. It is a technique that does not work very well for modes other than FM and where external amplifiers are used, where the output power required is less than the maximum rated power of the radio (actually, less than about 1.5 X the rated power).

Other manufacturers also have these problems. They address them in different ways.

In one example, the Yaesu FT8*7 series, there are two controls for each band set (HF, VHF low, VHF high and UHF), being drive gain and output power limit.

Another example is Icom’s IC910 where I understand that the power level control has a dual action, one is to reduce the amplifier gain and the other is to change the output power limit level. So it achieves the same kind of result as the Yaesu 8*7 series, and should result in no power spike when first transmitting.

In any radio, if the driver gain is too high, the output power may momentarily exceed the preset level intended from the radio and set by the power level preset feeding the ALC circuit. The time constant of the ALC circuit determines the attack and delay times but cannot prevent the power level rising above the preset value, momentarily, and that’s all we need to exceed the limits of a solid state amplifier device.

So in the 8*7 series you can set the gain level appropriately so that the radio cannot output any more than your chosen power level, and it is a matter of alignment procedure to adjust output limit and stage gain appropriately to get the result you want. They do (cleverly) offer three power levels and you can set the gain and the output power limit for each power level.

For a radio capable of 100w output it is never going to be enough to set the output limit (driving the ALC) to (say) the 25w level. As already stated, that will still result in a power spike while the ALC sets the output level to what the user requires (via the output power control). It is more obvious and easiest to see in the constant carrier modes like fm and CW.

If the drive level is sufficient to allow the power amp chain to produce 100w, then the initial output (on say CW mode) will be 100w, and if you have set the output limit to 25w, feedback via the ALC circuit will reduce the power to 25w. But the initial spike will always be there. It may only last a few milliseconds, but with solid state circuits it is not a matter of heat or averages, it is whether the input voltage exceeds the correct level at all, for even the first sine wave at 144 MHz, ie. for 1/144 microseconds.

What produces the spike? There is enough drive to the final amplifier for 100w. The output limit setting may be set for a lower power level, if so the ALC line is used to send a gain control voltage back to the gain controlled stage(s).

To make it impossible for a power spike to be produced, the drive level has to be reduced. We need to limit the drive to the power amplifier chain to whatever is needed to produce the nominal power level, whatever it is, 1w, 25 or 75. This could be done in several ways.

The first and typical way to reduce the drive level, when using audio source and ssb mode, as for WSJT and other AFSK type modes, is to reduce the audio level going into the radio.  This would work, but if the reduction in drive required is significant (more than say, 10 db) that decreases the signal level without reducing the level of noise and other inevitable spurious signals, including the suppressed carrier of the ssb signal.  Eg a carrier suppression level of 45 db may be specified by the manufacturer, referenced to its performance at full rated power.  By using the audio drive to reduce total output we are accepting that the suppressed carrier can remain at its current level, and that may be ok for some radios.

The second method of reducing the output is to use a high power attenuator between the radio and the external amplifier.  This attenuator would be in that circuit on receive mode too.  For EME use many operators using the separate receiver antenna input to the receiver, or use another receiver anyway.  But the impact of the attenuator on receive mode is another factor to consider.

Other options include:

  • Modify the radio’s internal gain in the transmitter chain, preferably in the section amplifying at the transmitting frequency.  Depending on the design of the radio, there may be a point where the final mixer output is fed to the amplifier chain, which would be a good place to insert a suitable attenuator.
  • Insert a voltage on the ALC line, setting the gain of the transmitter to the highest it is allowed to be – reducing the output level to the highest it can be to safely drive the external amplifier.
  • Bypass amplifier stages.

Some types of mods would render the radio incapable of higher power output, so would need to be reversed when moving the radio on to another purpose. Whatever method is chosen, it must prevent the drive chain from producing enough power to drive the output stage to full power.

Importantly, it should be done in a way that is absolutely foolproof.  A casual mistake by the operator that destroys the external amplifier is something to prevent entirely.

The metering on the radio would be meaningless if some of these options were taken.  Separate methods of metering the drive level and adjusting for best operation would be required.

This is not a plug and play application. We are using a radio in a way that is outside its designed purpose.

The inability of the TS2000 (or other radio) to be used without modification for lower power purposes is no reflection of its suitability for other purposes. All commercial radios are built for the most common use by the majority of buyers. When we apply these general purpose radios to special uses such as for EME amplifier drivers, we cannot really be surprised that they are not ideal for EME drivers “out of the box”.