Category Archives: equipment

South Black Range SOTA and park activation on 13cm band – 15th June 2019

Having received an offer from Ted VK1BL to help me find and fix the problem in my 13cm transverter, I spent an evening with him on 13th June. Moving through the various functional blocks in the transverter we found

  • The receiver was working quite ok, it was very close to the right frequency and was fairly sensitive, hearing -120 dbm from the HP sig gen pretty well
  • The output from the PLO was good and at a level of +7 dbm as recommended for the mixer
  • The output from the sequencer board, which includes attenuators and a level setting control for the IF signal, 144 MHz in this case, was working well and we calibrated that at -10 dbm for input to the mixer, with 0.5w drive on 144 mhz from the ft817
  • The output from the mixer and filter was at the expected level, about -13 dbm
  • The output from the tx IF amplifier/driver was +10 dbm, which was adequate for the power amplifier
  • The power amplifier had the correct negative bias and positive voltage on the correct terminals
  • But the power output to the antenna socket was zero.
  • The power output from the amplifier (before the relay) was about +35 dbm (approx 2.5 watts)
  • The relay board was examined and was found that the DC to the relay coil was intermittent. Resoldering the pins of the relay, a surface mount type, fixed that intermittent and made it a reliable connection. The output to the antenna socket was then +35dbm or 2.5w.
  • Transverter considered fixed.

With that result I discussed the possibility of an activation on Saturday morning to prove it in the field. Andrew VK1AD offered to activate Mt Stromlo and I decided to visit South Black Range. Coincidentally it was the day when bonus points commenced for VK2 summits above 1200m, so I half expected to find some snow on the higher parts of this summit, as it had recently snowed down to about 900m.

No snow, quite cold at about 3 or 4C when I got there, but it warmed up to about 8C by midday.

img_0829-1.jpg
FT817 in foreground, transverters and tripod holding 1296 yagi at rear

After initial contacts on 144 then 1296 we switched over to 2403 MHz and found we were able to make easy contact, my signal received a 5×8 report from VK1AD and I received his signal at an indicated strength 5.

Note: the distance of this contact was about 47.5 km, not bad for 2.5 watt transmitters. The locators of the two summits are QF44MQ (Stromlo) and QF44SN. The visual horizon is 35km so this is beyond “line of sight”. But how far over line of sight is it?

According to my iphone app DistBear the distance between centres of the two grid subsquares is 47.5km. So 2.4 GHz worked fine, well over the visual horizon. To get a more accurate distance I used the website https://sotamaps.org, using the “range mapping” option, we get a more accurate measure of the distance, at 48.7 km. I am sure there will be longer contacts made on this band using the same equipment.

The antenna in use for 2.4 GHz at my end is shown in the photo below attached directly to the 2.4 ghz transverter, was the SG-LAB PCB antenna, a 2 element HB9CV type on loan from Andrew VK1AD. The 2403 MHZ equipment was placed on a rock and turned so that the antenna pointed roughly towards Mt Stromlo, albeit through many trees nearby.

Two UHF transverters
The SG Lab transverter for 1296 is shown here sitting on the box containing the home made transverter for 2.4 ghz. These two transverters are, ironically, equivalent in power output and receiver function though they operate on different bands.

After completing the contact on 2.4 GHz I moved to HF and ran a few contacts on 7023 khz using the Pixie half watt morse transceiver (on a 50 x 50 mm PCB), then moved to the KX3 radio and ran contacts on 40m and 80m SSB and CW. I left the summit just after 12 noon, after spending 2 hours there. The temperature had risen to 8C by then.

Pixie PCB transceiver, battery, key, ATU, balun

Testing a Mountain Topper Radio (MTR) model 3B

Having seen the Steve Weber designed compact transceivers on the web and having seen an MTR owned by VK1FB, I was delighted to find one for sale on vkclassifieds.net.au recently.  After duly receiving it and waiting for my birthday to pass (due to my wife’s insistence on waiting for the actual day to receive gifts), I wanted to test it from home and learn the menu system, which like the radio itself, is very compact.

Using my home antenna, a fan dipole with elements for 80, 40, 20 and 10m, I connected the radio to power (a 3S Lifepo4), headphones and the antenna and turned it on.  It sent the number 4 in morse, saying it was on 40m.  I tuned it around the CW end of the band for a while and tried a few of the control functions.  Then I returned it to the default 7030 frequency by switching it off and on again (where have I heard that before?)

Then in the headphones I heard “cq sota de vk5cz” which was Ian at summit vk5/ne-095 in the north east of South Australia.  I listened to his contact with VK3PF and then heard him ask QRZ? (“who is calling”, or “is there anyone else there?”) to which I responded with my callsign.  He replied immediately with a good signal report.  I gave him a report and then told him this was my first contact with the MTR3B.  He acknowledged that and wished me good luck.  I returned the greetings and signed off.

Yes the new radio works despite being smaller than my morse paddle. It’s the blue box in this pic. Produces about 3-5 watts on 7, 10 and 14 MHz amateur bands. The Mountain Topper Radio 3B.

Ian/Buhd vk5cz posted to facebook a comment that this contact was the highlight of the activation, which was great to read.  And later he also published a video clip in which the contact can be heard taking place.

A day later I had the MTR connected again, this time on 14060.  I tuned it up to 14062 and there was a familiar callsign, VK5CZ, in contact with someone.  Looking at SOTAWATCH.ORG I saw that Ian had recently called CQ from another SOTA summit.  I waited until the contact was finished, then heard him send QRZ? and again sent my callsign.  Back he came with a 559 with QSB (fading) report, which was pretty good.  I told him it was the MTR again, which he was pleased to hear about.

Now I need a contact on the remaining band provided by the MTR, 10 MHz, for which I need to make some alternative arrangements as my home antenna does not have a suitable impedance on that band.  The MTR is designed for a 50 ohm non-reactive load.  I will route it through an antenna matchbox which can be adjusted to present a 50 ohm impedance to the transmitter.

So far so good.  I am very impressed by the MTR and look forward to many lightweight activations with it.

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.

 

Repairing RJ45 plugs on Icom mike leads

I have had problems with my Icom HM103 mike leads, caused by breaking the locking tab off the RJ45 plug.  This happens usually because the mike and lead are slightly tangled with other gear in my SOTA backpack, even though I use a plastic box to carry the small pieces like headphones, morse paddle, microphone and adaptors.

It also happened once before when I had the microphone of the IC706 stored in the central console of the car.  Pulling it out of where it was carried without due care for the plug  eventually damages it.

And without that little bit of plastic, the mike does not stay in the plug for very long.

Having broken the plugs on my IC703 mike and on the IC706 mike recently I decided to replace the plugs but add the shrouds or covers that protect the crucial locking tab.

The unprotected plug looks like this:

The plug with the protective shroud looks like this:

As a small issue found when re-terminating these plugs, I found that the shield connection was originally made using very small diameter heat-shrink or some other method of making the shield connection look like one of the other wires.  These plugs connect to the wires using connections that cut through the insulation.

I looked for heatshrink tubing that could be used for this purpose, but the smallest I had was labelled 1.5/0.8mm.  A shopping trip to my local computer/electronics parts agent in Yass produced no thinner option.  When compared with the existing wire, the diameter when shrunk was too large to fit into the slot of the connector.  So another method had to be found.

For the first mike I had cut the lead right at the point where the wire enters the plug body.  This created a problem with the shield connection and I had to try to form the shield into a narrow form so that it could slide into the appropriate slot.  After twisting it to create a spiral of multiple strands, it worked but I wished I had found a way to preserve the original insulation.   So when installing the second plug I didn’t cut the wire at the back of the connector, instead I cut the entire connector just behind the crimp point for the conductors.  That way I preserved as much as possible of the original shield wire assembly inside its insulation.

Cutting through the plastic plug body was simple enough but I did that in about 6 sections, ensuring that the wires were not damaged.

Result: a robust plug assembly on both my Icom microphone cables.

I am hoping this surgery will provide longer life for the plugs.

Footnote: I know blue shrouds don’t look right on these black cables and black radios.  But that does not worry me one bit.  And the mike is safe for children.

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”.

FT817 programming

I recently purchased a programming cable for use with the FT817. Plenty are advertised on eBay.

What I received:

  • a cable with plugs for the mini DIN plug for the CAT socket on the radio and a USB plug at the other end
  • A cd containing software

The USB plug is larger than a plain USB plug as usual for one of these USB-serial adaptors, as it contains the electronics to convert from USB to plain serial required by the radio.

The software on the cd included a driver for the USB adaptor and several other programs including a 2012 version of HRDeluxe, a digital modes utility and a few other programs. A specific program for the radio programming was not included.

The cd also included some “readme.txt” files and advice on how to work out which COM port was allocated to the adaptor, as most older software including HRD apparently is designed for COM ports rather than USB.

I installed the driver and it worked ok, revealing that COM9 had been allocated to the USB adaptor.

In HRD the only option appeared to be COM1. Same for a Yaesu programming utility written by a French radio amateur.  (817-mem from F5BUD.free.fr)

I opened the Windows control panel and found the details of the USB adaptor. In the tab revealing the com port allocated I double clicked (or right clicked?) the COM9 and was offered the option of changing it to another unallocated port. I chose COM1.

This still did not allow a connection to the FT817 to work. To see whether the USB hub needed to be restarted to get the new COM port to work, I unplugged and reinserted the USB adaptor cable.

Checking in control panel > device manager showed that the USB adaptor was now indicating COM1.

Launching the 817-mem Yaesu programming tool again, it now found the 817 on COM1 and I could then read the memory contents of the radio, save as csv, modify the csv with notepad++, then reload the csv and send it to the radio.

I set memory freqs for cw and Ssb frequencies on the hf bands and some net frequencies for VHF bands.

Programming the 817 direct using the front panel controls is quite feasible but having the memory channels saved externally is convenient. Also being able to clone and edit in an ordinary text editor is handy. Seeing the frequency and mode settings on a screen is better than having to scroll around them on the 817.

Fake sellers on VK Classifieds

Some recent ads on VKClassifieds.com.au have looked very attractive.  Some Icom and Kenwood high value gear (TS950Sdx and IC756 pro3) being offered at about 1/2 to 2/3 of its typical price in Australia.

An email enquiry to the seller, calling himself Donald [name withheld] of Wilmington Illinois USA and using an email address that looks like a callsign plus the numerals 73, returned some telltale responses.  He asked for payments via Western Union and UPS delivery.  And he used some odd English constructions in his wording.  My brother and I exchanged notes on the seller and agreed there was something fishy about the whole thing.

I posted an item categorised under Events, warning readers about unverifiable sellers and it only lasted an hour on the classifieds site.  I don’t know whether there is an automated system to delete items warning others of scams, or whether the site owner is very vigilant and deletes them himself. But in that time I received several confirming emails from others, one stating that it was a scam and he had already lost $200 to the scammer.

The callsign lookup in QRZ.com does match with the advertiser’s name, but the history of equipment used and the interests of that person do not match well with someone selling a TS950 or an IC756.  However the qrz.com entry does have a prominent comment saying that he had recently obtained the email address used in the advertisement.  This suggests that the email address was chosen to match the QRZ entry, then the QRZ entry was updated (QRZ has no security preventing this) and the comment about the email address was added, to allay any concerns readers of his ads may have about the legitimacy of the email address.  To me it does not match with common practice.  Nobody smart offers their email address in the clear on a website.  No thinking person wants the spam that results from doing that. My conclusion is that the whole thing is a minor example of identity theft, or at least “identity borrowing”.

Don’t send this fellow any money.  As usual, if it looks too good to be true, it is.