late success.

I made 3 2m EME QSO’s using a borrowed Kenwood TS-2000

I had the moon low but getting close to my neighbors – so not wanting to send around 15-30KW EIRP into their houses I had to quit.

N7NW, AD7TJ and W7MEM where all finished within 30 minutes – reports where about -22 to -26db.

so I will be QRV next few days during the best-cond with my borrowed TS2000 – but I really hope I can get my beloved K3 working soon.

elecraft k144xv frequency stability.

Okay – now to elaborate on this problem.

I bought my dream transceiver and have been generally pleased with the performance of the K3. It’s amazing how easy it is to interface to it and it’s a pure experimenters dream. Now I’m playing with LP-PAN adapter.

I had a DEMI 60W 2m transverter on order but decided to buy the K144XV-K module for the K3 as my amplifier only needs about 10W for a 500W output.

I was very eager to get on the air – but to my great dissapointment the K3 + K144XV has problems.

1. frequency stability after 50s transmit cycle. I see signals in RX drift up to 60hz after TX sequence. Littlebit less if I lower the drive.
2. Birdies – all around.

In this picture, you can see HA6NQ’s drace on 0Hz DF – and some birdies. After TX you can see everything moving.
I had reports from stations monitoring that my signal was also drifting.

When I ordered the K3+K144XV I saw no option of the RFLK board. So it must have just gotten available shortly after I made the order, or perhaps I just did not notice it. My K3 has the TCXO option installed.

As it appears, the K144XV is unusable on JT65B. I have not yet gotten the RFLK board delivered so the problem will hopefully go away when I lock the K144XV to the master XO.

Now in my oppinion, Elecraft should have a BIG warning sign when ordering the K144XV that it is unusable on JT65 – as they must have tested this. I got an answer from Elecraft saying that K144XV with the RFLK has been field tested and is working well. I’m not very happy to have spent $390 on a transverter where I could have spent little more and gotten a 60W transverter from DEMI (not that I know how that is performing). So Elecraft is selling a bad product there and then letting you spend more to fix it. The RFLK should just be a free upgrade from them!

Birdies:
I notices I had alot of birdies on 2m. I have my LCD monitors elevated on a small standoff table on top of my desk. When I pulled the K3 underneath the standoff I noticed that the birdies disappeared. Same thing if I turn off the LCD. This might point to an unclean power supply etc of the LCD – but the TS-2000 did not show this weakness. I started looking at the K3 – it has a open “grill” for the PA air intake. There we have the unprotected BNC connector for the antenna as well the HF. Not sure if this is the source – but it’s quite possible. I put a 50×50 aluminium plate on top of the table and grounded- problem went away. So the K3 is not very well shielded I think. These are just observations – no real measurements.

Now I hope hope hope the $89 RFLK board will fix this.

and darn, I was going to buy a IC-748PRO – but as it was rumored to be unstable on 2m in I decided to get the super stable K3 ūüėČ

not thrashing K3 – know it’s a great radio – but I put a question mark over the K144XV and that you have to pay more to get it usable.

73, Benni TF3CY

2M amp working – at least 250W out ;)

After now 2-3 months of constant pondering, ebay browsing, googling, pestering people with questions I have something to show Рamplifier is near completion !

5 watts in, 250w out quite good gain I must say – 15dB

Due to a faulty Bird element РI could not go all the way, also missing a bigger fuse.  so I will hopefully be able to borrow a bigger element to fully test the amplifier Рnow called Gandalf the gray!

here is a link to the project: http://www.tf3cy.is/2m-linear

Now I just have the issue that the MCU control board is rebooting when in XMIT – and I have some programming to do so I will get accurate voltage / current readings. Hope closing the RF unit will solve the reboot issue – perhaps I have to go to ebay and buy some old analog front panel meters ;/

– Benni TF3CY

 

Busy day – the pre-amp story continues.

Hi all

So I have been having big problems trying to get a pre-amp working inline.

The problem is that it has to be sequenced in and out correctly. Then the grand plan was to introduce a big linear amplifier into the equation.

I had several issues – I had no good relays, except for some big 24AC relays I bought by mistake on Ebay. Budget does not allow some cool vacuum relays – so I decided I would use what I have.

As I’m pretty lousy in designing proper DC circuits – I decided to use a project that was already underway, my Amplifier + rotor controller + sequencer that I have been working on. I had already put a vero bord into a small chassis and hooked a LCD + rotary encoder + some push-buttons. I even had some 7 port darlinton relay drivers on hand.

So toady I have put the relay into the chassis Рbuilt a relay buffer -with some relays to switch on 28V AC going into the BIG RF relays (not really RF relays) and gotten everything to work.

This is mainly because I use a small board called Teensy2++ Рthat houses a really powerful Atmega microcontroller. It has numerous in and out ports Р8 A/D converters and runs on 16Mhz Рso you can be really sloppy programming it Рwont notice it to much. And the best part is the bootloader that comes with the teensy Рyou have a small program running Рit will detect when you press the reset button on the teensy and upload a new code in 1-2s via USB. This is so much faster than ANY ICSP programmer I have tried and is perfect for someone like me. trial and error!

So I could just plow through writing the sequencer code upon my “testbed” with the LCD and¬†everything¬†hooked up. So now I have a working sequencer.

Only really bad hack was to intercept the PTT line from Signalink USB to the Kenwood. Time was short – I did a ugly thing… look at the picture. Probably have to order a new cable from Signalink.

Here are some pictures – This will hopefully be finished some day – preamp is working – now just the big test – try to xmit!

Finally – 2m EME success!!

I’m not a single yagi station anymore! After a really disappointing¬†night – only be able to decode one signal I decided to get the other yagi and mount it horizontally. This meant for some last-minute fixing. I found a small¬†carpenter¬†shop that made solid shafts out of oak. I got some cosmetically flawed shafts for little money and they now make the tips of the horizontal boom. I made trusses to strengthen the boom. This is a bit hard for the small rotor but he can manage this. During last night we had pretty strong winds and the antennas where bouncing quite a bit – I was mildly concerned if the wind force would increase as I would not be able to lower the antenna.

I can now add one JT65B QSO to the “long” list of 2M EME contacts!

This was my 2M EME contact #1 and EME contact #4 !!

This could possibly the first 2M eme contact from a TF native station. There are rumors that a another TF station was active some decades ago – but I have never gotten that 100% confirmed.

I finished the QSO with K5QE pretty much without any issues Рjust sent a wrong sequence once. But from there I could not decode anything Рgot some shorthands but it was like a total blackout. I visually inspected the heading of the antenna repeatedly РI did a CQ CQ run and got good reports on 100W РBut I was unable to hear anything. This was either some issue with my RX or a very bad case of faraday rotation. I did not have a pre-amp installed but that could not explain the really bad RX as I was getting quite good reports -21 to -25dB.

I will use the day to try to get the pre-amp working .

The station is now:

  • TS-2000 – 100W -internal pre-amp
  • 25m CableExperts feedline X-1318
  • 2x 2m5wl
  • Yaesu G-5600 rotor system AZ/EL
  • Pre-amp to be used is from WA2ODO

here are pictures:

QRV on 2m EME … just slightly

I decided to jump the gun as the weather is so good now…

I put up a 2m5WL yagi, have to have it vertical polarized. I have a view from ca 100¬į east to 250¬į – Got az/el ¬†control.

Having issues getting the pre-amp inline and the power amp to work togeather. coax is from “cable experts”.

1200W 6m – 2m power amplifier based on the motorola AR313

I needed a power amplifier for 6m EmE, so after looking around I found that my father TF3T had 4 unassembled AR313 kits from Communication concepts lying around, he also had a PCS4 splitter/combiner. This he bought some 15 years ago. They are based on the MRF141G “gemini” tranisistor. http://www.communication-concepts.com/ar313.htm

As I needed QRO asap this summer, I decided to build two modules and combine them with a combiner I already had. Also I did not have a powersupply to drive 4 modules at the time. The amp was built and worked well on 6m. It was not until this winter I got interrested in 2m EmE, the plan was changed and now I would get the amp working on 2m as well. This really just meant building a small relay board to switch between two low pass filters.

Power supply:

basic specifications:

  • Input voltage: 220-240V (jumpable)
  • Output voltage: 4x 28v
  • Output current: 4x 25A max (limited at 23A)
  • Maximium power rating: 3KW
  • based on 723 voltage regulator + 20x 2n3055 output transistors.
  • 150ms slow start is¬†accomplished¬†using control from a PIC 16F877A microcontroller. (using 10Ohm resistor)
  • LCD display that shows current and voltage per channel and cuts out the PA and Power supply if over voltage or over current status is detected. It’s bit slow as the processor is running at 5Mhz so the reaction time is around 10ms.

So basically this is a 3KW linear power supply built around a 3KVA toroidal transformer woven by Airlink transformers (UK based). It’s a heavy transformer, 17Kg and I got it delivered to Newcastle where I was on a business trip, bought a small cabin-case for it and took it through BA flight to London and then to Iceland. There is a loophole in the on-board luggage rules at BA, only dimensions, no weight restrictions.

As the power amplifier has 4 PA modules, each operating at 28v/22A I decided it would be easier to build the power supply with 4x 20A outputs, rather than 1x 80A output.

I’m using the standard 723 regulator with a 2n3055 in a¬†Darlington¬†pair configuration, 1 driver and 5 bypassing.

The PSU has a slow start using a relay that shorts a 10 Ohm after around 200ms

The PSU is controlled by a PIC control board that uses it’s 8 AD inputs to monitor voltage and current. I use a PIC 16F877A as I just happened to have few lying around. Current is measured using a standard op amp in a differential configuration.

I decided to use a inductor on the output and use the resistance in the 16AWG wire as the shunt, both for current sense and current limitation.

for now, here are some pictures, I will update this later perhaps with schematics if someone is interested :

The amp is based on the AR313 . I have already the amp working at 600W, but I’m adding two more modules to give a combined power of 1200W.

here are pictures of the current work:

It’s not pretty, but in tests it puts out 1200W on 6m. I don’t have the ability to fully drive the amp on 2m , but it’s going up to 600W, but I see it’s not very efficient on 2m – that worries me.

The 2m low-pass filter can been seen there in the back, it uses RG142 coax cable as capacitors, close to 1pF per 1cm, so each of the capacitors is 18cm of RG142. It was modelled in Elsie, and used a miniVNA analizer to test it.

The amp is being built from the ugly design of my first 600w 6m amp, ¬†so I look at this as a test bed for the moment. I have a nice chassis that I want to mount the amp in later. I’m also working on a nice sequencer to control relays and the pre-amp. That is coming – but I think I will test the amp on some nice EME over xmas. ūüėČ

update: 22/12/2010:

Tested the amplifier on 6m – 1200W without saturation, can overdrive to 1500W. Power supply heats up well and after a 50 second xmit the transistors are cool, only thing worrying me is the 30 ohm balancing resistors are heating up -(50-60¬įC). Luckily I have 10x 25ohm 50W on it’s way from ebay (russian made). I could only drive the amplifier up to 200W on 2m but the Yaesu 723R is just to weak to drive the amp, I need around 40W on 6m to fully drive the amp, but I only get about 6w to the amp due to some mismatch in the splitter on 2m.

End of a very nice stay in Grímsey.

We had a wonderful time at the Island. We where welcomed by the lovely people that live in Grímsey. We will definitely visit the island later on, perhaps during the IOTA weekend next summer. I made some 600 contacts, mostly on 20m SSB, some on 10m. We had some heavy aurora activity over the weekend so fewer contacts where made on the lower bands. TF3SG still made some contacts, and one JA QSO was made on 80m.

Conditions where strange on 10m. Had a big opening into Spain and Portugal, but going over my log I see that I logged a single QSO with Trinidad and Tobacco on 10m I did not notice that when I made the QSO, would be fun so see that confirmed. I did not hear any US station though. I was just using the 43ft vertical with a tuner, so not a very efficient antenna for 10m.

73, Benni TF3CY