Archive for the VHF Category

Remote station update

Posted in VHF on 5 February 2017 by iw0ffk

A brief report of the changes in the remote station system.

The relays to control the mains of the whole station and the PSU of the linear amplifier have been replaced with solid state relays like this one:

ssr

The relays are controlled via WiFi by an ESP8266, I added a small display just to monitor the temperature of the amplifier and to read the IP address.

esp

Some update has been made also on the web interface:

10GHz update + first “DX”

Posted in VHF on 15 December 2016 by iw0ffk

The annoying difference of frequency between TX and RX has been solved by stabilizing the supply of the local oscillator with a DC-DC converter. There was a small voltage drop due to the high current of the TX-RX coaxial relays (600 mA…)

First test with Silvano I0LVA, QRB about 50 km easily worked in SSB also with minimum power (50mW).

The surprise was during the Vecchiacchi Memorial Day of 4 December, Cesare I6XCK in JN63QO QRB  of about 215 km with the mountains in the middle, worked in CW directly, no RS. I received I6XCK with a clear 529 for the whole duration of the sked, but I had to wait a bit and repeat the report/number/locator several times to complete the QSO probably due to about 10dB of difference of RF pwr. I think a PA is needed…

jn61fs_jn63qo

I’m always free for any reasonable sked on 3cm.

10 GHz, state of play

Posted in VHF with tags on 17 November 2016 by iw0ffk

Over the past few months I acquired some parts needed to complete the Eyal Gal transverter. I had to build the filter placed just after the TX mixer that has been done by using 15mm pipe caps.  The local oscillator feeds the two mixers (TX and RX) with a 6dB directional coupler and a buffer amplifier.

The sequencer has been made with a simple circuit (IK5ZWU) and adapted to the Eyal Gal. The signal “TX Inhibit” is used to avoid any RF coming from the FT-817 during the changeover. In RX the Eyal Gal’s amplifier is disabled and his gain is set to the minimum.

txrx_seq_pcb_01

20161112_164036_hdr

The “ALC” signal simply sets the gain level of the output amplifier. With the FT817 set to maximum output power on 432 MHz (4 Watts) the trimmer R11 is regulated to obtain little more than 1 Watt. By lowering the FT817 driving power, the 10G power will be lowered to 600, 250 and 50 mW

Up to now I had only one SSB QSO, with IK0EQJ, and I discovered an annoying difference of some kHz between the RX and TX frequency. Probably I have to separate the power supply of the local oscillator from the transverter.

First steps on 3cm band

Posted in VHF on 16 September 2016 by iw0ffk

Two years ago in 2014 I bought from an Israeli surplus store an Eyal-Gal unit, model 6075 with range 10.0 – 10.85 GHz. This module has a LNA and a mixer for the RX path and an amplifier with huge gain and discrete power for the TX. It needs few other parts to become a complete transverter: local oscillator, mixer, bp filter and two relays for the TX/RX changeover. For the local oscillator I used a 100 MHz OCXO with a crystal at 99.36 MHz, manufactured by Eisch-Kafka Electronics, as a reference for a PLL-DRO to obtain 9936 MHz. This permits to convert 10368 MHz to 432 MHz and use the FT817 as IF.

Here the module tested in RX and TX in the LTG lab:

 

Finally this summer I had the time to install the dish on the roof, an old tv-sat 85cm dish and a feedhorn.

20160905_19_55_01
I still need some parts to complete the TX section, but at least I can receive and testing the band.

For now I received 4 beacons directly IQ0RM/B JN61fw, IW0REF/B JN62hj, IQ0AH/B JN40qw, IT9CIT/B JM67lx and IQ5FI/B in rain scatter.

Sporadic-E summer 2016

Posted in VHF on 17 July 2016 by iw0ffk

IW0FFK_E21EIC

Till now this summer is a bit short of multi-hop openings on 6m for my location especially toward USA and Caribbean area. Fortunately there was a good opening to Asia during the CQ WW VHF contest. The Thai hams are allowed to transmit on 50 MHz only during this contest, 16 and 17 July, so working the Thailand was a good shot.

Remarkable 50 MHz QSOs:

E2X in OK06 DXCC #196

HS0AC in OK04
E21EIC in OK03
E20QVD in NK99

DU7/PA0HIP in PK10

Worked also a new country distant only 1000 km to my station, so I had to wait a short ES skip:
5A1AL in JM62 DXCC #195

I was not much active on 144 MHz this year, but thanks to the great Android application ESsense  by PE1NWL linked to the DXrobot, I was warned promptly for the funny 18 June ES opening.

I had QSO with about 25 Ukrainian OMs on SSB and CW but the nice part was when the few kHz around 144.300 became crowded by neighbors callers so moved to 145.550 on FM mode and worked a good number of OMs transmitting with a vertical antennas and mobile transceivers.

 

Powermaster, how to read data via RS232

Posted in Electronics, VHF on 2 June 2015 by iw0ffk

powermaster

The “Power Master” is a digital RF power meter produced by Array Solutions. The coupler is separated from the display, useful when the amplifiers are away from the shack.

It has a RS-232 DB9 plug and can be connected to a serial port of the personal computer to read the FWD/REV Power and SWR with his control panel software called “Power Master Basic”.

Unfortunately this software runs only in Windows, if one needs to read the data in Linux or OSX (or in Windows with custom software) the Power Master’s RS232 port has to be activated, then the power can be easily read, parsing the ascii string coming out from the wattmeter.

To enable reading via the serial port, the undocumented command is:

0x02 0x44 0x31 0x03 0x43 0x30 0x0d 0x53 0x00

Total 9 bytes, the numeric notation 0xNN indicates an 8-bit value expressed using hexadecimal format.

When this command is received, the Power Master starts to send the data (example for 128W forward power and 1.11 SWR) :

(0x02)D,128,0, 1.11,0;0;0;0;0(0x03)4C

Hope this helps.


This morning good opening on 50MHz with East, heard some JA stations and worked a new country: Malaysia.

9M2TO_IW0FFK

9M2TO in OJ05 #194

Update spring 2015

Posted in VHF on 31 May 2015 by iw0ffk

To catch up with the blog status:

50 MHz worked 3 new countries:
9G5AG Ghana (March) #191
3B9FR Rodriguez Is. (April) #192
5Z0L Kenya (May) #193

On 144 MHz no activity at all and 432 MHz few QSOs during major contests just to give points to friends.

In few days, we hope, should be released a license for 2015 to operate on 70MHz band.

That’s all.