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The OCFD antenna has worked well, and I've even tuned it on 160m, but the model and the resulting FT8 QSO's are directly related. It's known as a Skywarmer, and therefore the NVIS radiation means 1500 miles max, so I had to look at what I could do. There is no room where I could make a full 160m OCFD, but on the short leg, I do have a few metres to play with so looked at what I could find.
The outcome is the data at www.qsl.net/df1hf/OCF_160m.htm and the work done by DF1HF.
It all looks very simple, with a 50mm PVC pipe, 125 turns and pop that on the short end, with a 4-5m tail. This set of dimensions need to be changed as I have 55mm pipe in stock after a Screwfix mix-up when building the QFH NOAA Antenna.
The translated values for 55mm is 115 turns, so that will result in about 20m of cable needed, plus the 4-5m tail.
The result will replace the wire to dacron cable insulator, pass the dacron through the coil and run the tail along and down the tree if needed.
The resulting MMANA GAL model
The antenna analyser sweep
When starting with the AEA PK-232, there are a few commands that may come in useful especially in the pursuit of an HF Packet Station. The first is the default configuration, which I paste into my PuTTY Command line once I've made contact with the PK-232 via Serial. This may be useful for you, or you may decide the options are different ;
mycall <CALLSIGN>
VHF off
HBAUD 300
EXPERT ON
packet
daytime YYMMDDHHMMSS
BTEXT <CALLSIGN>, <CALLSIGN>-1 MBX [LOC]
CText Welcome to <CALLSIGN>PK-232, I'm not here right now, Please leave a message on <CALLSIGN>-1 Maildrop.
Mtext Welcome to <CALLSIGN>-1, PK-232MBX Maildrop
BEACON EVERY 90
mymail <CALLSIGN>-1
passall on
8Bitconv on
constamp on
mdigi on
mproto on
mstamp on
xflow off
maildrop on
mdmon on
mon 6
MAXFRAME 1
PACLEN 60
DWAIT 0
wide off
Packet Commands
MailBox
Is the STA LED FLASHING ? Check MailBox Server, you have a message.
cmd:mdcheck
You have mail.
List Messages
(AEA PK-232M) 18396 free (B,E,K,L,R,S) >
l
Msg# Size To From @ BBS Date Time Title
3 PN 84 <CALL><CALL>04-Jul-20 14:14 test from portable station
Read Message
(AEA PK-232M) 18396 free (B,E,K,L,R,S) >
READ 3
Msg# Size To From @ BBS Date Time Title
3 PN 84 <CALL><CALL>04-Jul-20 14:14 test from portable station
test message into MBX for <CALL>-1, TEST TEST TEST
/E
Delete Message
(AEA PK-232M) 18396 free (B,E,K,L,R,S) >
k 3
*** Done.
(AEA PK-232M) 18536 free (B,E,K,L,R,S) >
cmd:
Create or Leave a message
cmd:mdcheck
(AEA PK-232M) 18396 free (B,E,K,L,R,S) >
s ALL
Subject:
Welcome to <CALL>
Enter message, ^Z (CTRL-Z) or /EX to end
<MESSAGE FOR ALL TO RECEIVE>
/EX
Message stored as # 1
(AEA PK-232M) 18172 free (B,E,K,L,R,S) >
The Pye Shaver Mic, there's something about the form. Is it the reminder of the 1970's Professionals TV series (Ok, that was the PocketFone 8 but looks similar), or the fact that it looks like nothing else in the Radio world ? I don't know but when I saw such a thing exists I knew I wanted to have one as a functional microphone in my shack. Formerly made for Pye PMR sets, the configuration of the mic does not lend itself to the modern Yaesu, so some degree of engineering needed to be done but the aim was to re-use as much of the microphone as possible whilst making it a good FM Repeater Mic, maybe going further with some audio filtering to give SSB tailored audio too. Let's see how far it goes, but this has plenty of scope for expansion !
Fig. 1 Opened Pye Shaver Microphone
The Microphone
Purchased on Ebay for £15, it was in nice condition, 6/10 with lots of glue residue and well used plastic shell. The Orange button had faded to a lighter orange but the microphone grill was 9/10 and internally as new. Internally, the quality and feel is excellent as would be expected for an AM PMR in the 70's. Good gauge metal frame and well engineered PTT, switching and PCB mount. The Mic mount in rubber was in good condition too, holding a 10v, 10mm insert. 4 wire + shield curly cable terminating in a lock connector.
Fig. 2 & 3 Internal Pye Shaver Microphone highlights (PTT and PCB)
The Plan
Create a Electret, Powered Microphone for connection to a Yaesu Radio, taking inspiration from the MH-31 Modifications by M0UKD / M0GEO and other advice from across the internet on the use of Electret inserts. Main requirements are for good FM audio input, some filtering via passive components, and correct output level into the Mic stage of the radio (FT-847)
The Parts
Choosing an Electret insert sounds easier than it actually is. Do you go for a 50p, Cheap insert with no datasheet, or look at the Panasonic WM-range for a few Pounds. Based on the Buy Cheap, Buy twice principle the Panasonic route looked better. Now, Which one ? WM-3x, 5x or 6x ? Piling through the datasheets for these discontinued items it looked like the WM-62 was the most used in pro audio, and also had a good up to 10v performance. It was only 6mm though and the original mic holder was 9-10mm diameter. The WM-52 looked like it covered almost all the requirements, but then I could not source easily. The WM-54B was sourced, being the WM-52A with the legs soldered on. Whilst I didn't need the legs, the would help with the soldering if nothing else.
Oddly, I didn't have an 8.2k Ohm resistor, so a 10k and 47k in parallel made a good substitute.
Fig.4 Pye Shaver Microphone bay (with microphone element removed)
The Circuit
The circuit, based on the M0UKD MH-31 modification, the Panasonic WM-54B was connected as per the following diagram. The aim was to try to re-use the Pye PCB that is internal to the microphone, either by replacing the components and/or re routing tracks. Whilst I tried to realign the original PCB, it was such a lot of re-engineering and long traces that I thought that RF would become an issue, so the PCB was replaced with some strip board, cut to size and drilled to fit into the space.
Fig. 5 Original Circuit Diagram for the Shaver Mic (From Pye Manual)
Fig. 6 Original Circuit Diagram inside the Shaver Mic.
| Wire Colour | Old Function | New Function | Yaesu Pin |
| White | 10v | 5v | 2 |
| Red | Audio + | Audio + | 8 |
| Blue | PTT | PTT | 6 |
| Green | GND | Audio - | 7 |
| Shield | GND | GND | 5 |
For PTT, the switch will now switch Pin 6 to ground pin 5, so the PCB trace will be cut and jumpered to GND.
The audio signal now will be passed out of Pin 8, (Mic +) and Pin 7, (Mic -) but will have a drop resistor for the incoming 5v, and a DC block capacitor.
The Circuit
The 8.2k Ohm resistor works in series as a voltage divider with the internal 2.2k Ohm resistance of the Insert, delivering 1v into the microphone element. The 1 uF capacitor filters the DC component and passes the audio signal into the radio via the curly lead.
The Finished PCB and Internal Wiring
The final PCB is here, where the circuit providing the Microphone supporting components and cross connection to the curly lead meet.
*** PCB Pic
This is a tidy install inside the microphone, and apart from the Yaesu 8-pin, there are no signs it's been converted into something else which was the plan. I suppose I could lay out a purpose built PCB for this, but the prices and numbers when I'd want 3 PCB's max seemed beyond reasonable. Strip board will do for now, and it's working. I've got the Gerber's if I change my mind though, or I have another PCB order going out.
Clean-up
I wanted to clean up the Orange PTT, it had broken down due to Sunlight, so I used the 3 grades of Novus Plastic Polish both manually and using a dremel mop. It cleaned up ok, but may keep an eye on getting another mic in better shape on Ebay in the future.
On-air Performance
In the excitement (No, I don't get out much) after metering out the circuit with the multimeter to check for shorts, dodgy soldering and stray wires, all was found to be good, and stable.
I then plugged in the microphone to the FT-847 for a few calls, with monitor switched on. First call into EA8DHV resulted in a good steady 59 signal, and no repeats. Second call into LZ1UBO resulted in a good QSO with unsolicited "Broadcast Audio" report. The Monitor audio from the radio also sounded a good audio signal was being sent into the radio, but listening to yourself is always difficult. I'll organise some recording on my SDR, to see what it does sound like.
The Yaesu FT-847 Mic Gain is now only on 10 o'clock, which is low for any of the other microphones I've got such as the MD200-A8X which needs full Mic gain. On the Yaesu FT-2000, Mic gain is only on 10, but sounds good without going into setting up the processor.
The End
This is a pleasing result to a bit of a crazy idea, but an enjoyable project and an excuse to get the soldering iron out !
Now, what next because I have a spare insert...
Thanks to M0UKD for the initial circuit and work and M1GEO for his write-up of his Yaesu modification.
Where
20m - 14.105.000 Mhz
Lower Side Band - LSB
Depending on the device you use, this CF will differ. On a PK-232 TNC, this will be 14.105.510 Mhz because of the tones. You will see the waterfall on Soundmodem so can select the stream. I'll expand on this further down this page.
14.105.000 Mhz
- PK-232 (US) [2110/2310] = 14.105.510 Mhz
- Kantronics KAM [1600/1800] = 14.105.000 Mhz
- UZ7HO Soundmodem - Tune using Waterfall Beacons.
Who
Anyone with a HF transceiver or Receiver and a 20m Antenna, TNC or Soundcard and a PC.
Why
The technology before the internet and these days often seen as a novelty. It would be a shame to loose the skills in Packet radio, especially the HF DX Packet communications. TNC Equipment is cheap on Ebay or using a soundmodem is just a matter of the right cable for your PC to Radio.
What
Have a listen for the beacon calls, you should set these to 900 seconds maximum and then call back, either to the call or to the mailbox ID. Leave Messages or try to digipeat to another station beyond your reach ? All fun things to try on a Sunday morning in the shack.
How
http://www.vectorbd.com/bfd/packet/hfpacket.txt
UZ7HO Soundmodem
http://uz7.ho.ua/packetradio.htm
https://www.youtube.com/watch?v=q9evYp6HcdA
http://rickmega.com/NBEMS/UZ7HO_Setup.pdf
TNC