144 MHz for the KX2 Transceiver

Many times I have thought it would be nice to have 2 metres on the KX2, I do miss it from the FT817 days.

This bare board transverter was on Ebay from a Ukraine seller, the feedback was very good and it looked quite compact so for about $35, I ordered one.

Bare Board Transverter

It took about 4 weeks to arrive, but it was over the Christmas break, so probably not too bad.

Internals

It measures about 80 x 45 mm, a very suitable size for portable operation.  The power output is stated as 10 to 15 Watts, so not too shabby.

A metal case was then bent up using my home brew metal bender.
A relay switched attenuator

Boxed up

was grafted between the PCB and the transceiver side BNC socket.  I was satisfied that the leads were short enough not to cause a problem.

A 10dB attenuator is fitted to a stand off post to make it level with the relay.  The T configuration attenuator is made from paralleled 0805 SMD resistors so that the power rating is 1 watt.
The KX2 will be set up for about 500mW out so that the maximum drive level of the transverter is easily met.

The KX2 has some nice configuration options to suit transverters.  Parameters such transverter number (you can have several), power output, frequency offset etc. are easily configurable.  In fact, the default configuration was fine.
When powered up, the transverter worked straight off.  Power out was around 10 watts, more should be possible, but will wait until the linearity can be monitored.  Sensitivity seems ample as well.

Connected up

 

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Posted in Projects, radio communications, SOTA | 2 Comments

Mt McLeod VK3/VE-034 SOTA

Mt McLeod was on the unfinished business list after we ran out of day light a couple of years ago when it was summit 3 for the day and decided to turn back.
Kevin, VK3KAB and I decided to have another go, this time as an overnighter rather than a day trip.  We left Melbourne on Boxing day with a leisurely start of 11am and arrived at the fire trail gate on Crystal Brook Rd., off the Mt Buffalo Rd. about 4pm.   This would avoid the heat of the day.
There is very little space to park the car near the gate to the Mt. McLeod Firetrail and thankfully there were no other cars.

The walk took about 2 hrs 30 minutes to the Mt McLeod bush campground.  We had pre booked a campsite there for the princely sum of $13.60 from the Parks website.

The walk is about 8km to the Mt McLeod campground and about 1km further to the Mt McLeod summit (one way).  My pack weighed 19kg, including 5kg of water as we were not sure of water availability.

on the way

There is a signed alternative route to Mt McLeod that avoids a partial section of the firetrail.  This route roughly follows a contour line and avoids a small climb on the firetrail, although I am not sure it was worth it.  The track was a bit overgrown and there were fallen trees in several places.  The alternative route is incorrect on the maps that we had with us, see the plot from the GPS later.

The hike has a lot of ups and downs and with the higher temperatures we had on Boxing day, going was a bit slower than normal.  The campground is just a cleared area near a creek and marshy area with a pit toilet up the hill a bit.  There was ample water supply from the creek, so we could done without carrying 5 litres or so each.  We were the only hikers there and we did not see anyone else during the two days.

campsite

Mt McLeod from the campsite

The next morning we arose about 6am and took the radios to the summit.  As the day was predicted to be hot, we thought it best to get an early start and return to the car as early as possible.  Kevin set up a linked dipole from a squid pole on the summit, an I set up the loaded end fed on a mini squidpole tied to a tree.  I qualified on 20m and Kevin on 40m.  Conditions were fairly average.

The walk out was uneventful and took about 2 hrs 15 minutes with temperatures around 30 degrees towards the end.

I must have had my laces loose as my toes took a beating on the many downhill bits with them ending up rather bruised and painful!

After we returned to the car, we drove to The Horn and did a quick activation hand held using the KX2 and the Diamond RHMB2 loaded whip.  There where tourists everywhere so we activated just in the activation zone where the railing starts.

 

Summit views

Summit views

 

 

 

 

 

Trig

KX2

GPS track

Elevation Profile

Posted in Hiking, SOTA | 4 Comments

Handles for the IC-7200 Transceiver

Grab handles are a good idea for the IC-7200  for when the radio is taken out portable.  The problem is that they cost something like $120 as an accessory!  This is about 10% of the cost of the radio itself.

I had some 5 mm thick Aluminium plate, so out to the workshop to make a set.

firstly, to drill out the handle

 

Lots of holes were made with the bench drill to make the handle slot.  The inner was then knocked out and filed to shape.  Lots of filing here!

The cleaned up handles prior to painting

The mounting holes are also drilled out for the M4 bolts.  I used cheese head M4x12 bolts for the hole towards the front and M4x16 bolts for the two rear holes.  You could use counter sunk bolts for a better finish.

Next some grey primer was applied as the first coat.

Measurements

A final 3 coats of flat black paint for a nice finish.
The two rear bolts need a 3mm spacer between the handle and the radio.  These were made from some delrin plastic rod cut to 3mm lengths and drilled out to take the M4 bolts.

The handles fit nicely and should give the radio controls some protection as well when out in the field.

All finished

The look pretty good and saved a bit of cash!

Posted in Projects, radio communications | Tagged , , | 3 Comments

Diamond RHM8B Antenna Strain Relief

I came across this interesting part at the Tokyo Radio Fair last month.

It is a BNC strain relief for the popular Diamond RHM8B antenna, particularly when used with a PL259 socket adaptor on an FT-817.  If anyone has one of these antennas, you will know how fragile it is at the BNC plug end.
The strain relief is simply a small plastic tube that provides support to the main shaft of the RHM8B which is then supported by the outer of the PL-259 socket on the FT-817 rear antenna.

This is the coupler or strain relief, not sure what to call it!

 

 

 

The tube simply slides over the main shaft of the RHM8-B as shown below:
Once the tube slides over the PL-259 adaptor, it takes the strain from the flimsier BNC connector which always worries me.

The tube was 500 Yen (~ $6 AUD) at the Radio Fair, the supplier details are on this web link.

It provides some piece of mind in case the antenna is knocked or catches on something.  Of course it will only provide limited protection but it is certainly better than no protection at all.  It might be possible to make one using an electrical conduit coupler from a hardware store, although this unit is a reasonably tight fit at both ends.
Note that I have two PL-259 male to BNC female adaptors and only one was a good fit on the rotating threaded section inside the tube.

 

The strain relief tube on the back of the FT-817.

 

Posted in radio communications, SOTA | 2 Comments

Lightweight 2m Yagi for SOTA

With HF conditions poor at the moment,  2 metres with a bit of antenna gain is a good backup or main setup for SOTA.
I wanted to make this antenna very lightweight and easy to carry in the pack without damage.  This is the design I settled on.
The boom is 20mm PVC electrical conduit (Bunnings) and the elements are 2.4mm aluminium TIG welding rod (Bunnings).

The antenna is carried as a single length of conduit with the elements stowed inside the boom, sealing them in with a bung.  The driven element is connected directly to 50 Ohm coax with a BN-43-202 balun core to decouple the coax shield.

The antenna was modelled with Yagicad by VK3DIP.  The driven element was positioned for a compromise between gain and an easy match for a direct feed.  See element lengths and positions below.

The boom has 25mm hex M3 threaded stand offs (Jaycar) inserted through it for mounting the director and reflector.  The driven element has a 10mm threaded M3 Nylon stand off (Jaycar) with two 10mm M3 male/female standoffs screwed together to form an insulated driven element mount.  The element mounts fit tightly into holes through the boom and then fixed in with Polyurethane glue (Bunnings).

The elements consist of 2.4mm Aluminium TIG rod that is joined to a short M3 threaded bolt section so it can screw into the boom mounts with fingers.  The aluminium rod and the M3 thread are joined with screw terminal inserts.  Originally, I was going to use copper plated steel welding rod directly soldered into M3 male/female standoffs but these rods were too heavy for my liking.  It would have been a neater solution though.

As it stands, without the  coax feed connected, the Yagi weighs just over 200 grams.  The elements are a bit fragile, but they do have some spring before they stay bent.  They will be well protected inside the boom when in the pack.

The SWR is under 1.5 at 146.5 MHz which is fine for the simple match.  The coax feed uses a 1.5 metre length RG-178 terminated in an SMA plug for direct connect to a portable 2m radio.
The elements are colour coded with heatshrink to identify where they are to be screwed in.

The balun core is held to the boom along with tape and heatshrink.
The next step is to make a better element to thread arrangment.  The terminal block inserts seem fine for the moment though.  It doesn’t take long to unscrew the elements from the boom and stow them inside.
The last photo shows the yagi ready to pack away.  The total length is 1 metre, much the same length as the longer squid pole.

Posted in Projects, radio communications, SOTA | Tagged | 9 Comments

MFSK16 APRS Tracker

Over the past couple of weeks I have been running this  MFSK16 APRS HF tracker in the car as a breadboard on 40m.
I tossed up on whether to make a leaded or surface mount PCB, but ended up with a leaded board as most of the parts easily available were leaded.  The board isn’t too tight and could be made smaller.
The board came out at 75mm x 70mm, so it’s pretty compact anyway.  The next morning after assembling it, , it was in the car and under test for a SOTA day.
It worked pretty well for 1.5W on a Lipo supply with only 2 of the 3 BS170 FETs in the final.  It should put out 5W with the third one installed with a supply of 13V.  Several location reports were received by Gerard, VK2IO and gated to the internet.  The antenna on the car was a small loaded 40m whip on the nudge bar.

If we had a few APRS Messenger gateways in Australia, QRP APRS would be a lot more viable for say, SOTA expeditions.

 

 

 

Update_208-04-07:
The transmitter now has 3x BS170 FETS in parallel and makes about 3.5 Watts out at 13V.  I found a plastic enclosure in the junk box that is a very good fit.  For the 3.3V rail to supply the GPS and PIC, I used an LM2594 buck switcher to 5V and then a linear regulator to 3.3V.  I may ditch the linear regulator and use the switching one to supply 3.3V but for the moment, the supply is kept very clean with the addition of the linear regulator.  Current consumption at 12V is less than 40mA idle and could be reduced further by shutting down the GPS receiver between transmissions.  Mike’s code supports GPS shutdown.

Packaged up

Posted in Projects, radio communications, SOTA | Tagged , , | 7 Comments

Weak Signal Mode APRS

Over the past few weeks I’ve been experimenting with APRS Messenger, a great PC based application that uses weak signal modes for Automatic Packet Reporting System (APRS). Traditional HF APRS uses 300 baud packet data for APRS messaging which isn’t really suited to HF communications.

APRS Messenger is capable of decoding PSK63, PSK250, GMSK250, MFSK4 and MFSK16 and then sending them to the internet (iGate operation).  These modes are much more suited to HF than 300 baud packet.

Gerard, VK2IO (Sydney) and myself (Melbourne) ran some tests between our stations on 40 metres (about 700km) using the various modes with latitude and longitude encoded.  Using PSK63, I was able to lodge quite a few location reports with Gerard while only transmitting 500mW RF out.  Of course this was not consistent and in fact there were some times when we could not communicate with 20 W, although most nights this has been fine.   Wade, VK1MIC also popped up on PSK63 with 5W from an FT817.

PSK250 was not too far behind PSK63 in performance.  A PSK63 position report takes about 12 seconds, where a PSK250 report takes about 4 seconds.  At my location I have a high level of noise and also an electric fence ticking away and these modes coped well with it.

Of more interest was constructing a light weight HF APRS station for remote area hiking.  If there were a few HF weak signal mode iGates around the country, this could be viable method of remote area APRS.
Recently, David, VK3IL and myself did some remote area hiking and David had set up a VHF packet APRS to HF APRS repeater in his car.  This worked pretty well considering the terrain we were hiking in.  See his blog for details on the hike.

An even better modulation mode for weak signal APRS is MFSK16.   I came across this interesting project from Mike, N0QBH.  This was a low power, standalone APRS tracker using MFSK16 mode.
I ordered some parts and built one up on a breadboard.  For the PA, I just used a temporary 2N3866 amplifier that was producing about 60-70mW out from the DDS drive of about 1mW on 40 metres.
The unit was calibrated and put on air.  To my surprise, I received an email from Gerard, VK2IO to tell me he was decoding the occasional packet in Sydney!  Conditions on HF have not been all that good recently either!

Here is a photo of the rather messy lash up of the beacon.  When the 5 Watt PA / LPF is finished and working, I will do a PCB and try and keep it as small as possible.  The GPS receiver, processor and DDS are all running from a 3.3V supply.  Current drain is between about 60 and 120mA at 3.3V.  The PA is running from 12V.
Mike’s software shuts down the DDS and GPS between beacons to save power.  At present I have not wired up the GPS shutdown, so it is running all the time.
With a switching regulator, the whole thing should be quite low current at 12V or 3 cell Lipo.

It’s a mess but it works!

Here is the breadboard lash up of the beacon.  It’s certainly not pretty, but it works.  The GPS gets a fix pretty quickly indoors.

Posted in Hiking, Projects, radio communications | Tagged , , , , | 3 Comments