Thursday, 31 July 2014

Transatlantic MF WSPR

Conditions must have been good last night! This morning I found I'd received signals from two USA stations (WG2XKA and WE2XGR/3) but the biggest surprise was that my signals had been detected over there, by WD2XSH/17

 2014-07-31 04:28  WE2XGR/3  0.475653  -28  0  FN42ch  10  GM4SLV  IP90gg  4996  41 
 2014-07-31 02:50  WE2XGR/3  0.475653  -24  0  FN42ch  10  GM4SLV  IP90gg  4996  41 
 2014-07-31 03:20  WE2XGR/3  0.475653  -21  0  FN42ch  10  GM4SLV  IP90gg  4996  41 
 2014-07-31 03:12  WE2XGR/3  0.475653  -25  0  FN42ch  10  GM4SLV  IP90gg  4996  41 
 2014-07-31 03:54  WE2XGR/3  0.475653  -30  0  FN42ch  10  GM4SLV  IP90gg  4996  41 
 2014-07-31 01:14  GM4SLV  0.475725  -26  0  IP90gg  0.2  WD2XSH/17  FN42pb  4958  279 
 2014-07-31 01:24  GM4SLV  0.475725  -30  0  IP90gg  0.2  WD2XSH/17  FN42pb  4958  279 
 2014-07-31 03:00  WG2XKA  0.475720  -26  0  FN33lq  1  GM4SLV  IP90gg  4950  42 
 2014-07-31 03:10  WG2XKA  0.475720  -24  0  FN33lq  1  GM4SLV  IP90gg  4950  42 
 2014-07-31 02:50  WG2XKA  0.475720  -25  0  FN33lq  1  GM4SLV  IP90gg  4950  42 

Two spots of my tiny WSPR signal were picked up by Dave (AA1A) using his special experimental call WD2XSH/17 in Marshfield, Massachusetts. He must have a good RX setup!

I'd already spotted John WG2XKA a few nights ago, and it's great to see more from him, and also great to see five spots from WE2XGR/3 (John, W1TAG) in Holden, Massachusetts.

A good night on MF, still in summertime.

Saturday, 26 July 2014


It was a busy night on 475kHz WSPR - many stations in Europe active and more in RX only mode. Best DX for me was again with IW4DXW - we both "exchanged" spots over a 1927km path.

My best DX in the RX direction was to get 4 seprate spots from the USA - WG2XKA - run by John WA3ETD - in Pittsford, Vermont at a distance of 4950km.

Here is a list of each station either heard by me, or who heard me, overnight last night

 2014-07-26 01:52  WG2XKA  0.475722  -23  0  FN33lq  1  GM4SLV  IP90gg  4950  42 
 2014-07-25 20:42  EA3NE  0.475732  -24  0  JN11an  0.5  GM4SLV  IP90gg  2094  355 
 2014-07-25 22:20  GM4SLV  0.475728  -19  0  IP90gg  0.2  IW4DXW  JN64bw  1927  146 
 2014-07-25 21:40  IW4DXW  0.475605  -16  0  JN64bw  100  GM4SLV  IP90gg  1927  337 
 2014-07-25 21:28  GM4SLV  0.475729  -27  0  IP90gg  0.2  EA2HB  IN93ah  1886  181 
 2014-07-25 22:30  GM4SLV  0.475728  -28  0  IP90gg  0.2  SP5XSB  KO02ld  1642  113 
 2014-07-25 21:06  GM4SLV  0.475726  -19  0  IP90gg  0.2  DH5RAE  JN68qv  1578  137 
 2014-07-25 21:40  DH5RAE  0.475751  -23  0  JN68qv  0.2  GM4SLV  IP90gg  1578  329 
 2014-07-25 23:44  DJ0ABR  0.475760  -29  0  JN68nt  0.2  GM4SLV  IP90gg  1576  329 
 2014-07-25 22:42  GM4SLV  0.475727  -25  0  IP90gg  0.2  DJ0ABR  JN68nt  1576  137 
 2014-07-25 20:44  F1AFJ  0.475703  -13  0  JN06ht  1  GM4SLV  IP90gg  1503  356 
 2014-07-25 20:38  GM4SLV  0.475726  -26  0  IP90gg  0.2  F1AFJ  JN06ht  1503  174 
 2014-07-25 20:56  GM4SLV  0.475725  -23  1  IP90gg  0.2  OH2SWL  KP20uj  1485  78 
 2014-07-25 22:00  GM4SLV  0.475737  -24  0  IP90gg  0.2  DF6SM  JN58ct  1475  145 
 2014-07-25 21:16  GM4SLV  0.475726  -27  0  IP90gg  0.2  F59706  JN07th  1455  171 
 2014-07-25 20:58  DK6NI  0.475672  -23  0  JN59ln  0.1  GM4SLV  IP90gg  1426  331 
 2014-07-25 21:00  DK2DB  0.475641  -12  0  JN48fw  0.5  GM4SLV  IP90gg  1409  337 
 2014-07-25 21:06  GM4SLV  0.475727  -16  0  IP90gg  0.2  DK2DB  JN48fw  1409  149 
 2014-07-25 21:06  GM4SLV  0.475725  -20  0  IP90gg  0.2  DF8UO  JN48ex  1403  149 
 2014-07-25 22:56  F6HCC  0.475678  -24  0  IN87hs  0.1  GM4SLV  IP90gg  1395  4 
 2014-07-25 20:56  GM4SLV  0.475723  -25  0  IP90gg  0.2  SP2OVY  JO94hg  1372  110 
 2014-07-25 21:16  GM4SLV  0.475729  -22  0  IP90gg  0.2  DK7FC  JN49ik  1366  147 
 2014-07-25 20:42  F5WK  0.475652  -18  0  JN18hp  0.2  GM4SLV  IP90gg  1319  350 
 2014-07-25 20:38  GM4SLV  0.475725  -26  0  IP90gg  0.2  F5WK  JN18hp  1319  167 
 2014-07-25 22:00  GM4SLV  0.475727  -24  0  IP90gg  0.2  F6CNI  JN19qb  1284  164 
 2014-07-25 21:46  DH0PAZ  0.475662  -23  0  JO30nm  0.05  GM4SLV  IP90gg  1210  337 
 2014-07-25 20:38  GM4SLV  0.475724  -29  0  IP90gg  0.2  DH0PAZ  JO30nm  1210  150 
 2014-07-25 22:20  GM4SLV  0.475727  -28  0  IP90gg  0.2  SM2DJK  KP03au  1182  61 
 2014-07-25 21:36  GM4SLV  0.475726  -29  0  IP90gg  0.2  G3XKR  IO70ux  1048  191 
 2014-07-25 22:08  GM4SLV  0.475728  -19  0  IP90gg  0.2  G8JNJ/A  IO90hx  1033  180 
 2014-07-25 22:08  GM4SLV  0.475728  -27  0  IP90gg  0.2  PI4THT  JO32kf  1030  147 
 2014-07-25 20:38  GM4SLV  0.475724  -24  0  IP90gg  0.2  PA3ABK/2  JO21it  1014  155 
 2014-07-25 20:40  PA3ABK/2  0.475740  -1  0  JO21it  0.5  GM4SLV  IP90gg  1014  340 
 2014-07-25 21:06  GM4SLV  0.475727  -19  0  IP90gg  0.2  DG3LV  JO53gv  1011  129 
 2014-07-25 20:48  DG3LV  0.475786  -27  0  JO53gv  20  GM4SLV  IP90gg  1011  319 
 2014-07-25 21:36  GM4SLV  0.475726  -22  0  IP90gg  0.2  G6AVK  JO01ho  972  171 
 2014-07-25 21:32  G6AVK  0.475762  -27  0  JO01ho  1  GM4SLV  IP90gg  972  353 
 2014-07-25 22:08  GM4SLV  0.475728  -17  0  IP90gg  0.2  M0PPP  IO93gm  751  180 

Here's the 4 spots of WG2XKA :

 2014-07-26 02:14  WG2XKA  0.475722  -27  0  FN33lq  1  GM4SLV  IP90gg  4950  42 
 2014-07-26 02:04  WG2XKA  0.475721  -25  0  FN33lq  1  GM4SLV  IP90gg  4950  42 
 2014-07-26 01:58  WG2XKA  0.475721  -23  0  FN33lq  1  GM4SLV  IP90gg  4950  42 
 2014-07-26 01:52  WG2XKA  0.475722  -23  0  FN33lq  1  GM4SLV  IP90gg  4950  42

A map view of the transatlantic crossing:

Friday, 25 July 2014

Return to MF

I last used MF under the old UK Special Research Permit, on 501 - 504kHz, in November 2011 after experimenting on the band since July 2007. Since that time the WRC has produced a new band worldwide at 472 - 479kHz. Not all administrations have released this new band but there are certainly more countries with access to MF now than when I was last using it.
I had a chance CW QSO on 5MHz with Chris G3XIZ, one of the MF stalwarts, earlier in the week and we discussed the idea that I might come back to MF. I got thinking about the good and interesting times I had between 2007 and 2011, with many CW contacts with Finbar GI4DPE and later EI0CF, and the interesting one-way tests between Shetland and Finland with Paul-Henrik OH1LSQ. He would now have access to MF and could now transmit as well as receive, so now we'd be able to have in-band two-way QSOs instead of cross-band or one-way (report by email) tests.
I dragged my MF transmitter from under the stairs and set about testing it and retuning the PA stage from 501 to 472kHz. It was soon producing 100W into test load. 

Next I retrieved the MF ATU (basically a tapped loading coil and an impedance matching transformer) and put it at the feedpoint of my current HF inverted-L. It didn't take long to tune & match the antenna - although it was much shorter, electrically, than the previous MF antenna - needing an extra 200uH of inductance to get it to resonance. After a day of testing I replaced the antenna with a new inverted-L, 11m high with a 25m long top-loading section. This initially resonated at 360kHz with the same tuner settings, a big increase in capacitance due to the extra top-loading. Removing the additional inductor and retuning got me a good match - the matching transformer ratio showed an overall resistance (mainly due to ground losses) of around 35 ohms. This is the same figure as when last used on MF, so the earthing system seems to be intact! 12.5W from the transmitter produced an approximate antenna RF current of 0.6A, which also implies a resistance of 35 ohms.
An approximate calculation, using Rik's excellent LF antenna Guide as reference, shows the expected Radiation Resistance to be 0.3 ohms
For 100W TX power I'd expect 1.7A of RF, and 867mW EMRP. This is an ERP of 1.5W and an EIRP of 2.6W. The UK limit is 5W EIRP. I have some way to go to reach the EIRP limit!
A couple of nights using WSPR, to give it a test... here's last nights "best DX" : 

 2014-07-24 21:22  GM4SLV  0.475724  -28  0  IP90gg  0.2  IW4DXW  JN64bw  1927  146 
 2014-07-24 19:10  IW4DXW  0.475605  -28  0  JN64bw  100  GM4SLV  IP90gg  1927  337 
 2014-07-25 02:58  GM4SLV  0.475731  -28  0  IP90gg  0.2  EA2HB  IN93ah  1886  181 
 2014-07-24 21:22  GM4SLV  0.475722  -33  0  IP90gg  0.2  DF8UO/A  JN37vo  1530  153 
 2014-07-24 20:22  F1AFJ  0.475704  -21  0  JN06ht  1  GM4SLV  IP90gg  1503  356 
 2014-07-24 20:32  DK6NI  0.475682  -28  0  JN59ln  0.1  GM4SLV  IP90gg  1426  331 
 2014-07-24 21:24  DK2DB  0.475641  -6  0  JN48fw  0.5  GM4SLV  IP90gg  1409  337 
 2014-07-24 21:22  GM4SLV  0.475724  -24  0  IP90gg  0.2  DK2DB  JN48fw  1409  149 
 2014-07-24 20:46  GM4SLV  0.475723  -28  0  IP90gg  0.2  DF8UO  JN48ex  1403  149 
 2014-07-24 20:38  GM4SLV  0.475726  -30  0  IP90gg  0.2  DK7FC  JN49ik  1366  147 
 2014-07-24 19:58  F5WK  0.475652  -26  0  JN18hp  0.2  GM4SLV  IP90gg  1319  350 
 2014-07-24 20:46  GM4SLV  0.475725  -22  0  IP90gg  0.2  F5WK  JN18hp  1319  167 
 2014-07-24 21:44  GM4SLV  0.475723  -18  0  IP90gg  0.2  G3XKR  IO70ux  1048  191 
 2014-07-24 22:16  GM4SLV  0.475724  -18  0  IP90gg  0.2  G8JNJ/A  IO90hx  1033  180 
 2014-07-24 21:10  GM4SLV  0.475723  -27  0  IP90gg  0.2  PI4THT  JO32kf  1030  147 
 2014-07-24 18:30  GM4SLV  0.475726  -31  0  IP90gg  0.2  PA3ABK/2  JO21it  1014  155 
 2014-07-24 18:40  PA3ABK/2  0.475740  -3  0  JO21it  0.5  GM4SLV  IP90gg  1014  340 
 2014-07-24 20:50  DG3LV  0.475786  -25  0  JO53gv  20  GM4SLV  IP90gg  1011  319 
 2014-07-24 20:58  GM4SLV  0.475725  -21  0  IP90gg  0.2  DG3LV  JO53gv  1011  129 
 2014-07-24 21:10  GM4SLV  0.475723  -26  0  IP90gg  0.2  G3WCB  IO91rm  975  176 
 2014-07-24 22:16  GM4SLV  0.475724  -15  0  IP90gg  0.2  M0PPP  IO93gm  751  180 
 2014-07-24 22:02  M0PPP  0.475698  -16  0  IO93gm  5  GM4SLV  IP90gg  751  0

I've set up a "grabber" using my Perseus SDR which can cover the full 7kHz of the new band. To improve the resolution of the images I've split the band into two sections. The grabber is here:

Next I plan some antenna improvements. I'm limited to the height I can raise the vertical section of the antenna, but I can probably add more top loading, and hopefully improve the ground system to reduce the loss resistance. Reducing ground losses leads to an increase in RF current flow in the antenna, and as radiated power is proportional to the square of the antenna current, every extra ohm shaved from the ground loss increases the ERP. Dropping to a ground loss of 30 ohms would improve the E(I)RP by around 0.6dB. Adding more top loading would improve the current flow, increasing the radiation resistance and also reduce the system losses by reducing the losses in the ATU (as the antenna would need less inductance to bring it to resonance) and this would also add to the ERP. I'm wary about adding too much wire, as I know from previous experience what a Shetland winter storm can do to wires hanging in the air...

Monday, 14 July 2014

Night of Nights 2014

I've followed the story of the USA's "Maritime Radio Historical Society" and their restoration of the former coast station KPH at Point Reyes/Bolinas in California over the last few years. For background reading they have a nice website : and various You Tube videos:

Each year, on the anniversary of the initial closure of KPH they bring the station back to the air for "Night of Nights", and have pulled in other former Morse Coastal stations who still have facilities, such as WLO in Alabama. This year I wanted to see if I could hear any of the action.

KPH and most of the other stations are on the West Coast, and mid-summer, with static crashes and little darkness, means hearing them on MF or the low HF bands is unlikely. VOACAP showed a chance on bands between 8 and 17MHz. WLO in Alabama was likely to be a little easier to hear, although again, 500kHz was never likely to be successful.

The event was due to begin at "one minute past 5 pm" PST - one minute after the anniversary of the shutdown on July 12th 1999.

This is 0001 UTC which is 01:01 BST!

The MRHS published the planned frequencies of the participants in their newsletter

I programmed the frequencies into my HF radio and settled down for a late night looking for weak CW.

At 2045 UTC I heard "NMC de KKUI" on 16736kHz and then shortly afterwards "WLO do KKUI" also on 16736kHz. KKUI is the callsign of "American Victory", a museum ship anchored in Tampa, Florida.

Later I began to hear WLO sending it's "wheel", the repeating channel announcement listing their listening frequencies. I could hear them on their 8MHz, 12MHz and 16MHz channels, although shortly afterwards the 12MHz channel fell silent.

Here's a recording from 16968.5kHz

At 0001 UTC I began to hear, very weakly - affected by static crashes and all manner of polar fluttering etc. a barely detectable Morse signal from KPH on 17016.8  and in parallel from KFS on 12695.5  and 17026.0

The best recording I could manage is here

Not good, but with a bit of imagination you can hear "VVV" and "KPH" and a few other things drifting out of the noise.

At 0030 UTC I again heard "American Victory" KKUI calling KPH, and heard the KKUI side of a contact with the former coast station. Quickly checking the frequencies used by KPH showed nothing I could read, so I've only got the KKUI side of the QSO:

After this QSO with KPH I heard KKUI calling the partner station of KFS, and again captured the KKUI side of the exchange:

There were also amateur stations active at KPH and WLO - K6KPH and W4WLO respectively. I heaerd WLO's wheel giving the frequencies, but heard nothing of W4WLO - but there was a big amateur radio contest in full flow (the IARU HF Championship). I did hear a station, K4JJW, calling K6KPH briefly on the amateur 17m band (18097.5kHz):

I lasted until 2am local time before calling it a night. I'm sure more traffic would have been audible later, especially on the lower channels, 12MHz and 8MHz.

I checked the channels at around 0700 UTC and heard weakly the final closing message, not really readable, but the odd snatch was clear enough to determine what the signal was, on one of the 8MHz channels used by KPH/KSM/KFS

Looking at WLO's channels and I found their closing statement, ending with the first message sent by Samuel FB Morse: "What hath God wrought?"

I enjoyed knowing that these old transmitters were back on the air, imagining the lights dimming on each dot and dash when keying multiple high power transmitters in parallel. It's a pity that none of the European power houses of the past have been conserved and could join in this celebration and remembrance of the history of Marine Radio using Morse Code. At least we still have the MRHS to keep CW alive.

Wednesday, 9 July 2014

Update on VHF/HF Cross-gate

The Voice Operated Squelch used in the first test version was okay for detecting human speech, but suffered from false triggering on static crashes from thunderstorms. Further research showed that the kit I got via eBay is a copy of the Naval VOS-4 design :

This is also the squelch circuit used by Steve G4HPE in his experimental HF-Internet Gateway:

I decided to try the "original" syllabic squelch circuit, as published in 73 Magazine in 1982 and is a copy of the Motorola "Constant SINAD Squelch" which was originally part of their MICOM range of HF SSB radios:

This proved to be much more successful, and since it's adequately documented it is possible to make changes to component values to alter the behaviour to suit different purposes. The Jet Propulsion Lab modified this circuit to use on a link feeding NASA-Select downlink audio into a VHF Repeater:

I'm planning to replace the V/UHF link transceiver - currently an FT817 which gets warm even when on Low Power during a long "HF to UHF" transmission - installing an FT8900R which is capable of higher power, and also has a cooling fan. The external "data" interface is identical to the FT817 and therefore can easily be swapped in without re-making cables.

Since this is effectively "Remote Operation" under Clause 10 of the UK Amateur Licence, the 70cm port can run at any power (up to the maximum allowed by the license) as the "communication link" to operate the main station

10(1) The Licensee may conduct Unattended Operation of Radio Equipment provided thatany such operation is consistent with the terms of this Licence. Additional restrictions whichapply to the Unattended Operation of Beacons are specified in Schedule 2 to this Licence.  
10(2) Subject to Clause 10(3), the Licensee may also conduct Remote Control Operation ofRadio Equipment (including, for the avoidance of doubt, Beacons) provided that any suchoperation is consistent with the terms of this Licence.  
10(3) This Clause 10 does not permit the Licensee to install Radio Equipment capable ofRemote Control Operation for general unsupervised use by other Amateurs.  
10(4) Any communication links used to control the Radio Equipment or to carry Messages to or from the Radio Equipment in accordance with Clause 10(2) must be adequately secure so as to ensure compliance with Clause 3 of this Licence. Any security measures must be consistent with Clause 11(2) of this Licence. 
10(5) The use of any such communication links referred to in Clause 10(4) must be failsafesuch that any failure will not result in unintended transmissions or any transmissions of atype not permitted by this Licence. 
10(6) If this Licence is a Foundation Licence or an Intermediate Licence, and the Licenseewishes to establish communication links to operate the Radio Equipment in accordance withClause 10(4), then the Licensee may only do so using wireless communication links and theLicensee may only use the amateur band allocations detailed in Schedule 1 to operatethose links. Any such communications links shall be subject to a maximum power level of500 mW pep e.r.p. 
10(7) Only where this Licence is a Full Licence, Full (Reciprocal) Licence, Full (TemporaryReciprocal) Licence or a Full (Club) Licence, the Licensee may make use of anycommunications links (including, for the avoidance of doubt, the amateur band allocationsdetailed in Schedule 1) to establish the wireless communication links referred to in Clause10(4).

Clause 10(4) is taken care of by

  1. Using DCS on the 70cm port, with "code" which is is regularly changed.
  2. Using DTMF to control the talk-through, which requires a 4-digit "PIN" number before the instruction to enable/disable the HF-UHF and the UHF-HF talkthrough. The ability to enable each direction separately allows for "HF Monitoring" without enabling "HF Transmit" and only enabling the UHF-HF direction when two-way comms is required.
The link can't be "encrypted" as that's forbidden by the general licence conditions, but I think the steps of "DCS" to access the UHF port and "DTMF" to enable/disable talkthrough meet the terms of clause 10(4):

10(4) Any communication links used to control the Radio Equipment or to carry Messages
to or from the Radio Equipment in accordance with Clause 10(2) must be adequately secure
so as to ensure compliance with Clause 3 of this Licence.

I've used the remote link to have QSOs with GM4WMM by operating the home station on 5.298MHz while I was located approx 26km from home, and the system worked well.

Thursday, 26 June 2014

First Place in CQWW

I dabbled in the CQWW SSB Contest last year and submitted a log. I've just checked the CQWW results and it appears I came First in my country for the Single Op, All Band, Low Power category!

Since Shetland is a separate country for CQWW, and there were only 3 active stations in the contest

Saturday, 21 June 2014

HF - VHF Cross-gate

I've been playing with the idea of being able to cross-band repeat between HF and VHF, after reading about the Barrett 2062 x-gate on their website:

Initial tests last year, just using the simple RF-level squelch from the HF transceiver to trigger transmit PTT on the VHF port proved rather poor, as fairly readable HF SSB signals were not causing the squelch to open. What was needed was a syllabic squelch - as found on professional HF SSB radios - for the HF port. Using the VHF transceiver's normal FM squelch is perfectly okay, of course.

I found various designs for "Voice Activated Squelch" circuits and then stumbled on a kit on eBay:

I bought a couple and built one to play with, in series with the audio from the HF receiver. It certainly worked much better on weak SSB than an AGC/RF level squelch.

The Barrett device also used DTMF (or SELCAL) to activate the talkthrough, so I thought I'd try and emulate that, and found another kit that would fit the bill:

I built the kit, but never tested it. I consigned both the VOS board and the DTMF board to the "in progress" pile, and forgot about them for 12 months!

Today I thought I'd resume the project......

After modifying the VOS board to trigger a relay, which could be used as a PTT source for the VHF radio, I wired it all up on the bench, and it works, I even get the revertive CW signals from the DTMF board sent back over the VHF port when the commands are issued to turn the relay on & off.

Adding a few switches to manually inhibit talkthrough, or to override the DTMF driven active/inhibit relays and it's all boxed up and working. I need to add some LEDs, to show what's happening inside. The one main difference between this box and the Barrett 2062 is that the Barrett device allows remote channel changing of the HF transceiver via the VHF port - something that's not immediately possible in this simple version. I guess a PIC and some programming and it might be possible to send CiV signals tothe IC7200 on receipt of specific DTMF sequences, but that's starting to get more complicated!

Using the IC7200's rear-panel accessory socket also has the bonus that the Speech Processor is available, unlike the old IC718 (where the processor only worked on the front panel Mic socket).

Now I need to try it out on the air, 5MHz would seem the ideal place to test these things - so I need to set up a sked with a willing volunteer...


After much local testing, and quite a bit of listening, I heard MM1MAJ/P on 5403.5kHz operating from a SOTA summit near Loch Leven. Weak, barely moving the S-Meter on 5MHz but triggering the syllabic squelch in the x-gate reliably so I thought I'd try a call to him. He came back instantly and gave me a 5/7 report. The only minor issue is the few seconds the HF squelch takes to drop at the end of an incoming transmission, but that's no real problem. I'm quite pleased it worked on the first real on-air QSO.

I've thought a bit about HF channel changing, and the only simple solution seems to be to use one of the DTMF relays (there can be up to 6 relays) to trigger an up/down channel change via the Mic socket (pin 3). Unfortunately the "pulse" option of the DTMF board toggles a relay for 1/2 a second, which is too long for a single channel step. I will think about a pulse shortening circuit (differentiating the 1/2 second pulse and using that to click a relay for a brief instant.....?).

Or just leave the HF transceiver on one frequency.

I will try to monitor 5298.5kHz as this channel tends to be lightly used, and the regular occupants tend to mess about with odd setups too, so perhaps it's a good place to try some tests.

I've found it necessary to leave the DSP Noise-blanker turned on to remove the occasional (weak) clicking from a distant electric fence, which would occasionally trigger the syllabic squelch. I also find that night-time lightning static crashes can also be a nuisance, as they tend to occur at roughly speech pulse rate, I guess. Using the DSP Noise Reduction and (for good measure) leaving the Auto Notch Filter engaged might just be enough to keep things usable.

A 5-minute TimeOutTimer on the V/UHF transceiver (an FT817) means it's possible to recover control should something (a long...long...over for example) hold the x-gate open in the RXHF->TXVHF direction. Once the V/UHF rig "times out" it's possible to send the DTMF "OFF" sequence and kill the x-gate until the long QSO on HF is over, or the HF channel can be changed.