50MHz RF survey of the Malvern Hills

After operation from Black Hill last weekend I decided to see how it compared with the other hills in the Malvern Hill Range. On Summer Saturdays there is a Bus from Worcester to Ledbury that stops at British Camp (which avoids the need of doing a round trip along the hills) to get to a car parked at British Camp. The bus stops next weekend so this was the weekend to try it. It was also good exercise being about 8km walk in total and rising to 1400'

As there was no contest this weekend comparison would have to be by looking at 6m and 2m beacons. Again using the KX3, but this time with the 6m extension on the whip antenna. The following is a summary of the 6m results

Black Hill GB3BUX 529 , GB3BAA 539, GB3MCB 549, GB3RAL 529

Pinnacle Hill GB3BUX 549 , GB3BAA 549, GB3MCB 559, GB3RAL 539

Jubilee Hill GB3BUX 519 , GB3BAA 539, GB3RAL 529

Worcester Beacon GB3BUX 519 , GB3BAA 539, GB3RAL 519

North Hill. GB3BUX 549 , GB3BAA 539, GB3RAL 519

GB3VHF on 2m  being to the East of all of the hills did not vary in signal strength. GB3BAA and GB3RAL similarly  are to the East and were little affected by location. I was a little surprised that RAL was consistently weaker than BAA. GB3MCB is South West and on any hill North of Pinnacle hill is blocked by the other hills hence its no show.

Pinnacle Hill looking South from Perseverance hill

Worcester Beacon looking North from Perseverance hill

KX3-2M KX3 144MHz Internal Transverter

The KX3-2m module is lower left

I ordered this during Dayton and it arrived this week after a 3 month wait. It took about 20 minutes to fit into the KX3. Measurements showed 2.5W output off 13.8V and the W5HN/B beacon was audible on a whip attached to the SMA antenna connector, so sensitivity seems ok.

After arriving in England I also tried out its vhf performance see http://g4fre.blogspot.co.uk/2014/09/144mhz-portable-backpacking-activity.html and http://g4fre.blogspot.co.uk/2014/09/50mhz-rf-survey-of-malvern-hills.html 

I originally also ordered a 4m transverter module, but after seeing warnings about the limited number of times the two RF cables interconnecting the modules to the KX3 could be plugged/unplugged, I gave up on the idea cancelled the order and reverted to the external 70MHz DEMI Transverter

Closeup of KX3-2m module

Lake Whitney State Park

After leaving Belton, rather than rush straight home I decided to go via the Lake Whitney state park. On the way up I35, on the north side of Waco I found the Colin Street Bakery cafe (the factory is in Corsicana...off the beaten track), so It was time for coffee and cake for lunch
Continuing on in glorious sunshine (yes the promised heat did arrive) the park was reached at 1400.  Paying the $5 admission I first explored the (closed) launch ramp but the ground surrounding the car park was too rocky to get the antenna base in. I moved to the area near the swim zone (noone was swimming ) and managed to erect the PAC-12 antenna with 4 radials. Again starting on 10m the SWR was at 1.5:1.

The CQWW WPX SSB contest was in full flow, but 5W to an 8' vertical doesnt stand a chance amongst the big signals and intermods on the band. (eg VK4KW was 59+20 on the vertical but the most response I got during 20 mins of calling was "WW2?" twice!  I struggled to work 10 stations in EA, LU, OH, VE6, VE7, W6 and W7. I tried fitting the 15m and 20m coils but those bands were not much better So I decided to give in and go for a walk round the lake trail. It was very obvious the Lake water level was low:-

 Rather than returning directly up I35E I took highway 77 (which runs parallel to I35E)  which goes through Hillsboro TX, Paris, TX (home of the concrete igloos) and Waxahachie (which promised BBQ downtown but had ran out!) before eventually getting on I35E and making it home.

Mother Neff State Park

It was time, after a 5 year absence for a trip to the Belton hamfest.  Rather than rush down and back on Saturday I decided to go down on Friday and visit another state park on the way. I chose the Mother Neff State park SW of Waco and NW of Temple, which claims to be the first ever state park in Texas. The trip down I35 was uneventful,Lunch was taken In Waco then the route west was started. Immediately thunder, lightening and hail started! There was a lot of ground water when I got to the Park. Putting $2 admission in the honesty box I followed the ridge and found a parking spot. At which point the clouds went away and the sun came out. I planted the PAC-12 antenna with the 10m coil next to the car and called a few stations with the 5W CW from the KX3. I had 10 QSOs with JA, F, FG, DL, the only escapees were a DU and VK4. Being sprint a group of brilliant red red cardinals put on a display, as did the hawk that sat on the fence next to the antenna trying to work out what It was. Time for tourism so I went and looked at the cave on the way out. The warden, having observed my "paid" sticker was closing the access gate at 1630pm but she gave me the combination so I could escape at 1900, giving me just time for Dinner after the HPSDR Teamspeak session at 2000

KX3 Noise reduction modification

Elecraft finally published details of the mod to reduce the noise heard in the receiver when turning the tuning knob, especially on 6m The document is at. http://www.elecraft.com/manual/KX3%20Tuning%20Noise%20Mod%20rev%20B3.pdf
Tonight I did the modification that basically cut 3 pins off the KXFL3 module and took 10 minutes to complete. The fix was very good and I now hear no noise on 6m or 10m, even in a low noise location

Radio Goodies Arrive

The USPS had a busy day delivering today!

The new side panels for the KX3 arrived and took only 5 minutes to fit (including finding the correct screwdriver). The perspex cover is on backorder but the side panels are already protecting the knobs

The "knurled whip" sleeves arrived from Budipole and now the whip on my active antenna doesnt wave around. I might be persuaded to make another PAC-12 Antenna now as it will be more robust.

The DFS30 multiplier to be used as part of the new W5HN 6m arrived from G4HUP in England in an impressive 4 days (faster than I get mail from Austin 200 miles south!)

Finally an MFJ 6m folded dipole arrived so I can test out the 6m beacon and keep an eye on the band!

The KX3, the fridge and the hairdryer

In my post on Jul 7 2012 I noted that frequency stability of the KX3 was not good enough for digital modes even on 40m. It had been pointed out that the KX3 was designed as a portable mountain top rig for use on SSB and CW and it was never designed to be highly stable

Since that time Wayne N6KR has done some investigation and has come up with a procedure to generate a custom frequency offset versus temperature table for the KX3 that the KX3 can use to adjust the offset. The procedure is at http://www.elecraft.com/manual/KX3%20Custom%20VFO%20TC%20rev%20A8.pdf

To do the procedure,  a highly stable (the XG3 isnt good enough!) 50MHz signal source is needed. Elecraft will sell you a suitable XG50 for the purpose but there has to be something in the shack. The K3 runs off a GPS locked 10MHz source so the fifth harmonic could be used? Initial tests showed the 50MHz level was not high enough, I needed a harmonic generator. Searching the parts bin I found an LF minicircuits mixer with connectors (intended for my 477kHz TRUE transverter). These contain diodes so they must generate harmonics. I found that driving the IF port with 10MHz and connecting the RF port to my 6m antenna produced a healthy 50MHz signal. good enough for the procedure

After making sure that I understood the procedure the KX3 was put in the fridge for 30 minutes. When removed the KX3 starts to warm up and the KX3 records the audio frequency of the tone against temperature (actually temperature a to d value...you can see what is happening in the KX3 utility programme as well as on the KX3 LCD) and stores it. To calibrate the upper temperature range (above KX3 ambient temperature) a hairdryer is used to heat it up. The procedure suggests until 52C but, being winter mine stopped at 43C which is adequate for the UK so I stopped calibration there.

After applying the calibration table It was great to hear the note of the 50MHz signal stay at around 550Hz all the way back down to 25C. The process was speeded up by putting the KX3 on a bag of frozen peas!

Next to see what the KX3 looks like on LF QRSS

KX3 Maintenance

Time to take the KX3 apart and address a couple of issues

I finally got hold of the KXBC3 Battery charger/Real time clock that was ordered Dec 28 2011 (11 months!). Took about 30 minutes to fit. Now I do not have to take the batteries out of the case to recharge them, but there is enough backup power on the board for the clock to remember the time for up to 5 minutes if the batteries are taken out.

While it was apart I took out the RF board to do the upgrade to take care of the lower dynamic range on 80/160m that was identified in the ARRL QST KX3 review. This involves removing 4 surface mount Inductors and replacing them with different values. The Inductors cost under $1 from Mouser Electronics. The modification took just 30 minutes. For the squeamish you can get Elecraft to do the changes for you  for $50 plus shipping each way as they consider it an "improvement" not a "defect correction"

Next I will do the extended temperature frequency calibration procedure to see if I can make it work on HF QRSS/WSPR without drifting. Fortunately this has to be done with the covers on

KX3 HF Band Decoder

Having had a KX3 for nearly 6 months now, the biggest handicap has been the lack of band outputs to switch external equipment (eg LPF in external PA, antennas etc).  These are standard on the K3 but are missed on the KX3. So Today I finished rewriting and testing the code for my RS232 Transverter driver to accomplish this. The writeup is at http://g4fre.com/KX3_RS232_hf.htm

K3 RS232 Band decoder

Having been disappointed with the ability of my K3 to readily provide outputs to switch VHF/UHF transverters I decided I needed a solution.

Initially I used some logic ICs to decode the band data on the rear panel ACC connector,  but having to reconfigure the interface every time I added or deleted a band was a right pain.  This was described at http://g4fre.com/k3vhf.pdf

Next I decided to use a PIC to do the decoding as it was easier to reprogramme a PIC chip than it was to redo the logic circuits. This decoded just 4 bands as it was intended for 4 bands HF, 6m, 2m and 70cm. This was described at http://g4fre.com/K3_PTT_sw.htm

Next I designed a circuit to decode the RS232 signals also available from the back panel. This looks at the 38400 Baud RS232 data and provides a 1 of 8 band output and a corresponding 1 of 8 PTT signal. It was designed for the 8 bands 144,432,23cm, 13cm, 9cm, 6cm 3cm and 1.2cm. This was written up at http://g4fre.com/K3_RS232_sw.htm . This worked fine for my station in the USA.  However I received a request to make it decode the 8 bands  4m, 2m 70cm, 23cm, 13cm, 9cm, 6cm and 3cm for use in the UK. So today I modified the code and tested it out and it works fine. This version is at http://g4fre.com/K3_RS232_UK.htm

I also tested it out on my Elecraft KX3. It worked fine, all we need now is for Wayne to write the software to support transverter mode in the KX3

KX3 on QRSS

Having made up the audio cables for the KX3 it was time to try it on QRSS (slow speed morse). As Bill W4HBK was running his QRSS grabber on 40m Friday night it would be possible to see the on air signal. The following is a capture from Bill over a 6 minute period

The upper signal (N4FRE) is the GPS locked ARDMEPT. The lower DFCW signal (WW2R) is from KX3.  Both signals have 4Hz frequency shift and are running 200mW  The drift on Transmit noticable on the KX3 and a little unpredictable; the pattern between different (even adjacent transmit period)  periods is not the  same

The following shows a comparison between the two signals over a two hour period. Each transmission is repeated every 10 minutes, synchronised to GPS. The good news is that the long term stability is good, It doesnt drift too much over the period BUT the bad  news is that the short term drift over a couple of minutes is not good enough for QRSS

Unlike the Elecraft K3 there is no provision to lock the KX3 to an external high stability oscillator. The KX3 uses the SI570 chip that is self contained. Looks like the KX3 will need a lock board for narrowband modes.

For the want of a KXBC3

Initial testing of the KX3 was using a set of 2300mAH NiMH cells I bought off amazon.com when i placed my KX3 order. Eventually they discharged forcing the KX3 to power down, (even after setting Vmin from the default 11V to the recommended 8.5V) but as the KXBC3 internal charger wont be available for a couple of months I needed an immediate solution. Looking on ebay I found an 8 cell NiMH charger for $20 shipped that would suit the purpose. I made sure it could accommodate 110 and 230V mains. Today it arrived so I can now again use the KX3 in a truly portable manner

Today is KX3 Construction day!

 The build started at 1015am after turning on the coffee pot.

Assistants ready for action

Front Panel Installed

Battery Shield Installed

Quality Audit #1

Double Supervision

Install ATU

Insert Roofing Filter

Battery container Installed

Insert Batteries

Very Happy Bear

Final Q.A. Inspection

Finished 1215, (including a coffee break). First QSO on 20m at 1330 after KX3 calibration and my Lunch!

KX3 Finally here

The KX3 ordered on 12/28/2011 at 10:33:00PT arrived this afternoon. I got the despatch notification 21 June saying UPS would deliver the package on 27 June. I was therefore surprised to find the package on the doorstep when I returned from the NTMS Tuesday lunchtime BBQ.


It will be a new challenge for Carol who has only previously built three Elecraft K3 

Happy Bear

Visit to Hamcom 2012

Just returned from the annual Hamcom Hamfest which was held in Plano, Texas.  As usual it was hot and clashed with the ARRL 50MHz to Light Contest

Elecraft were in attendance showing the recently released KX3 transceiver. They were currently still sending out kit radios ordered on the day that orders started being taken. Unfortunately mine was ordered on the 2nd day!

One interesting demonstration was using the I/Q data supplied by the KX3 to drive an IPAD to produce a panadaptor display using the ISDR app. As the 3.5mm audio input to an IPAD is mono and the I/Q requires a stereo input it cannot be used. This was overcome by using the I-MIC interface connected to the IPADs 30 pin connector via the IPADs USB camera adaptor

Unfortunately the ISDR software doesnt track the mode and frequency that the KX3 is tuned to.  However there is an app called HAMLOG which can track the frequency, but it currently doesnt interface to ISDR. The issue of how to connect the RS232 output from the KX3 to the IPAD which doesnt have an RS232 connector is solved by a device called a Pigtail available from Pignology LLC. This is an RS232 to WIFI converter which allows the IPAD to see the KX3 device. All I need now is the KX3 to arrive to try it out!

I also got to see the new Elecraft KAT500 500W Auto ATU which was smaller than I visualised. It only has the same footprint as the K3. It will be available from August.

I did finally give in and ordered the RemoterigII pair to allow me to remotely control one K3 with another K3 over the Internet without a computer. Sufficient RJ45 cables were found at the Hamfest to make the necessary interface cables.

To help the construction of a 472kHz bandpass filter for my 10MHz to 472kHz Transverter the opportunity was taken to stock up on a range of silver mica capacitors  on one of the outside stalls. The only other purchases were a speaker/mic for my IPAQ and an active GPS antenna for $5 each