SSTV on 2 metres FM
Everything you learned about SSTV on HF applies on 2 metres except the parts that matter: there is no ALC to set, no graceful degradation to rely on, no propagation to wait for, and — unusually — an actual band-plan allocation rather than a convention. It is also the easiest place to run a local picture net, because the signal either arrives perfectly or not at all.
Where SSTV lives on 2 m
The 144 MHz plan names the mode directly, and gives it far more room than HF does:
144.500-144.794 MHz 20 kHz All Modes
144.500 MHz – Image Modes Centre (SSTV, FAX, etc)
144.600 MHz – Data Centre of Activity (MGM, RTTY)
144.750 MHz – ATV Talk-backThe 20 kHz necessary bandwidth is the operative figure, and it is why FM SSTV is practical here at all — on 20 metres you have 2.7 kHz to work in.
Note what this is not: a channel reserved for you. It is a shared All Modes segment carrying data and digital voice as well, so the usual courtesies apply.
A word about 144.550
Open Signal ships with its dial defaulting to 144.550 MHz, inside this segment. Worth knowing before you use it: the band plan’s Note 8 records that AM usage is typically found on 144.550 MHz.
Nothing prohibits pictures there — AM and image modes are both legitimate in an All Modes segment. But if you want to be found by other SSTV operators, and to avoid sitting a five-minute transmission on top of the customary AM calling spot, 144.500 MHz is the frequency the plan actually points image modes at.
Do not use the calling channel
145.500 MHz is the FM calling channel. Calling on it is correct; sending pictures on it is not. An SSTV transmission occupies a channel for one to five minutes, and doing that on the frequency everyone monitors for calls is antisocial in a way that gets remembered.
Call, agree a working frequency inside the all-modes segment, and move — the same convention that applies to a long voice conversation.
Repeaters: no
- Timeout timers will cut you off partway through a picture, and a picture cut in half is not a picture.
- The extra receive-and-retransmit stage degrades the audio, which degrades the image.
- Many repeater keepers prohibit data and image modes outright. Check before assuming otherwise.
Deviation replaces ALC
On HF SSB you set drive by watching the ALC meter and backing off. FM has no ALC. The equivalent adjustment is deviation — how far the transmitted frequency swings — and the target is roughly 3 kHz.
- Too little: your picture arrives noisy even when the signal is full quieting, because the audio is sitting low relative to the receiver’s expectations.
- Too much: the receiving discriminator clips, producing harsh horizontal streaking, and you occupy more bandwidth than the segment allows.
FM is markedly less forgiving here than SSB, because there is no gradual degradation to hide a mediocre setting. Get it right once and leave it — the general method is in audio levels and ALC.
The trap on many modern rigs
Plain FM mode on a lot of transceivers takes transmit audio from the microphone only. PTT keys, the meter shows power, and you transmit an unmodulated carrier while your computer audio goes nowhere at all.
The fix is a DATA variant of FM plus a menu setting pointing the audio source at the USB codec. On the FT-991A that is DATA-FM plus menu 071, documented in the FT-991A setup guide; other rigs have equivalents under different names. If your 2 m SSTV is silent while HF works fine, this is almost certainly why.
The capture effect
FM receivers lock onto the strongest signal and suppress everything weaker. The practical consequence for pictures is a cliff: above threshold you get full quieting and a clean image, below it noise takes over quickly.
So VHF SSTV feels binary in a way HF never does. There is little point nursing a marginal path — either improve the antenna or accept it will not work today. What you gain in exchange is reliability: a path that works at all works every time, because nothing about it depends on the ionosphere.
That reliability is what makes 2 m good for local picture nets, club demonstrations, and — on 145.800 — the ISS.
SSTV on 2 m FM — FAQ
Where does SSTV go on 2 metres?
144.500 MHz is named in the RSGB band plan as the Image Modes Centre (SSTV, FAX, etc). It opens a shared All Modes segment running to 144.794 MHz with a necessary bandwidth of 20 kHz — generous enough for FM SSTV, which is why the mode is practical on 2 m and not on HF.
Can I use the 145.500 calling channel for pictures?
To call, briefly, yes — that is what a calling channel is for. To send pictures, no. An SSTV transmission occupies the channel for one to five minutes, and monopolising the calling frequency for that long is poor practice. Agree a working frequency and move.
Can I send SSTV through a repeater?
Generally you should not. Repeaters have timeout timers that will cut you off mid-picture, the extra link degrades the audio, and many keepers explicitly prohibit it. SSTV on VHF is a simplex activity.
Why does my FM picture look perfect or terrible with nothing in between?
The capture effect. An FM receiver locks onto the strongest signal and suppresses everything else, so above a threshold you get full quieting and a clean picture, and below it the noise takes over quickly. HF SSB degrades gradually; FM does not.
More about Open Signal
HF and VHF, same program
Open Signal defaults to 144.550 MHz out of the box and follows your VFO automatically once CAT is connected — so the logbook records the right frequency whichever band you are on.