Tips and Tricks

Simplex/Duplex

After attempting to help a couple of Foundation licence holders with the programming of their FT-991(A)s, I had to point out to them a term that all Radio Amateurs should be aware of:

All MF, HF, VHF, and UHF amateur radio uses simplex, or split-simplex.

The term "split" is often used on HF when a station is transmitting on a different frequency to their receive frequency. This is exactly how VHF and UHF operate when you are working through a repeater. To date, I have not come across a duplex system for Amateur Radio use. Systems that use duplex, such as mobile phones, tend to have a large frequency spacing. See the External link  UMTS Wikipedia page for an example of duplex spacing.


Inter-G

If you are new to the hobby of Amateur Radio, you may hear old-times on air referring to "Inter-G" and you are probably wondering what they mean. The term in an anachronism considering there are now more M call-signs issued than G call-signs. They are referring to the term Near Vertical Incident Skywave, or NVIS for short. NVIS tends to become available below 7 MHz, and with a suitable NVIS aerial (usually a horizontal dipole), you can work other UK-based Amateur Radio stations by bouncing your signals off the Ionosphere as if it was a giant mirror hovering over the UK. Under the right conditions, a station in the south of England will be able to talk to stations in Wales, Scotland, Devon, Cornwall, and Ireland with relative ease (depending on local QRM levels); and vice versa. The term should really be updated to Inter-UK or Inter-UK NVIS to avoid confusion.


S20/SU20

If you are new to the hobby of Amateur Radio, you may have heard people on 145.5 MHz and 433.5 MHz referring to S20 and SU20. Once upon a time, in the 1970s, they read the band-plan, then ignored all future changes. The terms for the channel names assigned to the VHF and UHF Amateur bands were replaced decades ago. As the RSGB survey pointed out, a lot of people are resistant to change. They also do not like to think of Amateur bands being channelised, as that is akin to Citizens' Band radio, and that is bad! (Not my words, I came from CB!).

If you decide to engage in a QSO with someone still referring to the VHF/UHF channels by their incorrect terms, you may also find they are using the wrong channel spacing, especially if they are using old PMR kit on VHF that can no longer be re-programmed. They might offer "down one" (a CB term!) and disappear 25 kHz down, whilst you, with your correctly programmed radio move 12.5 kHz down, and lose them! So be prepared to enquire if they are using the correct channel spacing.

If you have a particularly grumpy group around your QTH who are annoyed at all the young Foundation licence holders, using the 12.5 kHz channels instead of the older S10/S11 channels should ensure you are never pestered by them!

To help the newbie Ham, here are some useful charts with the correct names and frequencies.

VHF Channels
Channel Deprecated Frequency (MHz) Mode Comment
V16 S8 145.2000 FM/DV External link  RAYNET priority national usage | Tx to ISS (Rx 145.8)
V17 145.2125 FM/DV
V18 S9 145.2250 FM/DV RAYNET national usage
V19 145.2375 FM/DV FM Internet Voice Gateway (IARU common channel)
V20 S10 145.2500 FM/DV Used for slow Morse transmissions
V21 145.2625 FM/DV
V22 S11 145.2750 FM/DV
V23 145.2875 FM/DV FM Internet Voice Gateway (IARU common channel)
V24 S12 145.3000 FM/DV
V25 145.3125 FM/DV
V26 S13 145.3250 FM/DV
V27 145.3375 FM/DV FM Internet Voice Gateway (IARU common channel)
V28 S14 145.3500 FM/DV
V29 145.3625 FM/DV
V30 S15 145.3750 FM/DV
V31 145.3875 FM/DV
V32 S16 145.4000 FM/DV
V33 145.4125 FM/DV
V34 S17 145.4250 FM/DV
V35 145.4375 FM/DV
V36 S18 145.4500 FM/DV
V37 145.4625 FM/DV
V38 S19 145.4750 FM/DV
V39 145.4875 FM/DV
V40 S20 145.5000 FM only Calling frequency | FM only | Digital calling use 144.6125 MHz
V41 145.5125 FM/DV
V42 S21 145.5250 FM/DV GB2RS RSGB News
V43 145.5375 FM/DV
V44 S22 145.5500 FM/DV Rally/Exhibition talk-in
V45 145.5625 FM/DV
V46 S23 145.5750 FM/DV May be used for repeaters in other IARU Region-1 countries
V47 145.5875 FM/DV May be used for repeaters in other IARU Region-1 countries

Notes: 1. FM/DV means Frequency Modulation or Digital Voice. Once you have QSY'd off the FM calling channel, you are free to switch to either DMR, D-Star, or Fusion. Analogue deviation should be Narrow FM, or no higher than +/- 2.5 kHz.

2. All of the frequencies listed above are for simplex use only. They are not to be used with digital gateways; i.e. Pi-Star


UHF Channels
Channel Deprecated Frequency (MHz) Mode Comment
U272 SU16 433.400 FM/DV IARU Region 1 SSTV (FM/AFSK)
U274 SU17 433.425 FM/DV
U276 SU18 433.450 FM/DV In other countries IARU Region-1
recommend 433.450 MHz for DV calling
U278 SU19 433.475 FM/DV
U280 SU20 433.500 FM only FM calling frequency | FM only
U282 SU21 433.525 FM/DV
U284 SU22 433.550 FM/DV Used for Rally/Exhibition talk-in
U286 SU23 433.575 FM/DV

Notes: 1. FM/DV means Frequency Modulation or Digital Voice. Once you have QSY'd off the FM calling channel, you are free to switch to either DMR, D-Star, or Fusion. Analogue deviation can be +/- 5 kHz.

2. All of the frequencies listed above are for simplex use only. They are not to be used with digital gateways; i.e. Pi-Star

You may notice, from the new U-channel numbering, that the system has been created to allow a switch to 12.5 kHz spacing; thus there is space for U273, U275, et al.


Digital simplex

For completeness with the above, you may also wish to programme in a series of correctly spaced digital voice channels in to your radio(s). Yaesu System Fusion uses the full 12.5 kHz bandwidth, so it is important to always move in 12.5 kHz steps to avoid QRM with other digital voice users. It is very poor operating to only move 5 kHz above the calling frequency just because your digital mode does not use the same bandwidth.

Here are two handy charts of suggested VHF and UHF digital channel names and spacing. Data is taken from the RSGB band-plan.

VHF Channels
Name Frequency (MHz) Comment
VDV Call 144.6125 VHF Digital Voice calling
In other countries IARU Region-1 recommend 145.375 MHz
VDV 1 144.6250 May be used for Emergency Communications and Community Events
VDV 2 144.6375 May be used for Emergency Communications and Community Events
VDV 3 144.6500 May be used for Emergency Communications and Community Events
VDV 4 144.6625 May be used for Emergency Communications and Community Events
VDV 5 144.6750 May be used for Emergency Communications and Community Events

UHF Channels
Name Frequency (MHz) Comment
UDV Call 438.6125 UHF Digital Voice calling
UDV 1 438.625
UDV 2 438.6375
UDV 3 438.6500
UDV 4 438.6625
UDV 5 438.6750
UDV 6 438.6875
UDV 7 438.700

Programming FT-991(A) Memories

The United Kingdom uses a range of repeater shifts for the 70 cm UHF repeaters. The helpful Automatic Repeater Shift function in the FT-991(A) causes a problem when storing UHF repeaters with shifts more than 1.6 MHz, so it is best to switch both ARS options off.

Press the Menu button and using the multi knob, scroll to menu 084 and 085. Set both of them to OFF.

I use the ADMS programming software from External link  RT Systems to set the options and memories. The programming software is handy to restore the radio settings if a firmware update requires a factory-reset. You can also use it to re-arrange the four option buttons at the bottom of the screen. In memory mode, I have the SQL and MCH buttons to hand for easy adjustment and easy memory changes.

I have found it is better to disable the option in the ADMS software that automatically sets the offset splits (yellow circle):

ADMS prefs

... then set the split frequencies manually for the nearby repeaters, as in the example below:

ADMS memories

If you would like to re-use my memory layout (I have the VHF simplex channels matching their respective memory number), you are welcome to download examples from the downloads page to use with ADMS.


LDG AT-200 Pro II :: FT-991(A) Interface cable

I had an LDG AT-200 Pro II aerial matcher (they are not tuners!) to match my doublet dipole (changed mid-2018 for a FC-40 and long-wire) to the FT-991(A), and to switch to my Solarcon Imax2000 vertical (retired August 2017). LDG provide an interface cable to drive the FT-991(A). It is available in the UK for around £ 20. You can make one for around £2.50.

The details of the interface lead is here: External link  http://www.ldgelectronics.com/c/252/products/19/24/1

If you are UK based, you can source the parts needed from Combined Precision Components (or others):

External link  http://cpc.farnell.com/pro-signal/psg08320/3-5mm-jack-plug-3p-red/dp/AV19156

External link  http://cpc.farnell.com/pro-signal/psg03699/3-5mm-3p-jack-to-bare-ends-1m/dp/AV21895

The cable plugs between the LDG AT-200 Pro II's rear 3.5 mm port (black end) and the FT-991(A)'s REM/ALC port (red end). Using the lead means you cannot use the remote control keypad.

Remember: set Menu 143 TUNER SELECT to LAMP

When you wish to match your aerial to a specific frequency, press and hold the TUNE button on the LDG until the red LEDs (of the top bargraph) come together in the centre. The matching cycle will begin by the LDG commanding CW at 5 Watts from the FT-991(A). That will be increased by 10 dB for the mid part of the matching, then another 3 dB for the final match. The next time you use that frequency, the LDG should remember and automatically engage the necessary L and C relays.


FT-991(A) :: FAST

If you are manually scrolling through VHF with a 12.5 kHz step, or UHF with a 25 kHz step, the multi knob will jump 10x if you have the FAST button set.


How not to make a RF connector!

I detest the PL-259 plug and the SO-239 socket. I would be quite happy if they were banned, consigned to history, and replaced with the vastly superior N-type connector. As I am forced to use the SO-239/PL-259*, I make a point of using high-quality connectors that either clamp or crimp the braid. Cheap connectors are usually poor connectors. Avoid anything that has to be screwed on to the coax!

* Unless the equipment is out of warranty, then there is a chance the SO-239 will be replaced with an N-type socket.

July 2019 - I have repaired a Yaesu FT-767GX and an FL-7000 for local Radio Amateur (a G4 call-sign). Both units required the replacement of their memory batteries - easy enough. The FT-767GX had a keyer fault (blown input gate on Q60); and the FL-7000 had blown PSU transistors and a blown PA transistor. Having repaired the transceiver and amplifier, I was horrified to see this was the connection to one of the aerials:

Bad PL259
Click on the image to load a larger version (in a new window).

The inner pin rotates and the coax rotates with it! There is no electrical connection to the braid, despite the solder. This was expected to handle 400 Watts! Needless to say I cut it off and replaced it with a crimp PL-259.


Recommended connectors

I have used and recommend the following crimp connectors:

External link  ebay China RF 10x N-type for RG-213/LMR-400

External link  ebay China RF 20x PL-259 for RG-213/LMR-400

You will need the associated crimp tool:

External link  ebay China RF Crimp tool


Page updated: 13th September 2021

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