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Author Topic: 27.7000 SSTV and others 1750Z  (Read 327 times)

Offline IrvingtonVFD43

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27.7000 SSTV and others 1750Z
« on: March 01, 2024, 1758 UTC »
SSTV all over 27.7000 this morning, most of the stations doubling over each other. The last image may be my first Trans-Atlantic, or polar path SSTV image I have received.

Not to mention, 11/10 is hot here in Nebraska this morning! Got UK CB 27.781 very active. 10 meters reaching over the pond into UK, et., al.



« Last Edit: March 01, 2024, 1800 UTC by IrvingtonVFD43 »
All reception reports are direct into Norfolk, Nebraska unless otherwise specified.

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Offline Polar Bear

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Re: 27.7000 SSTV and others 1750Z
« Reply #1 on: March 07, 2024, 1828 UTC »
I was not aware that the rules were changed to allow Slow Scan Television on 11 meters...  Not that it is the Citizens Band because the Citizens Band does not go that high up in frequency...

Online R4002

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Re: 27.7000 SSTV and others 1750Z
« Reply #2 on: March 13, 2024, 1816 UTC »
I was not aware that the rules were changed to allow Slow Scan Television on 11 meters...  Not that it is the Citizens Band because the Citizens Band does not go that high up in frequency...

It's the "freeband".  The CB rules for the USA do not permit SSTV.  However, the CB radio service in countries like Germany, Czech Republic and others actually do allow data modes, digimodes, fax/SSTV - either on all of the available channels, or on specific channels.  Germany and the Czech Republic have 80 legal CB channels available.  Channels 1-40 are identical to the European standard channels - which are identical to the US FCC 40 channels / American CB channels.  Just like in the USA - AM, FM and SSB voice modes are permitted on channels 1-40.  Digital modes are permitted on certain channels (see below).

Channels 41-80 are actually lower in frequency, and only FM (narrow FM) and digital modes are allowed.  Digital modes include FT8, ROS, PSK31, SSTV and regular old AX.25 packet

Channel 41 is 26.565 MHz
Channel 42 is 26.575 MHz
Channel 43 is 26.585 MHz
Channel 44 is 26.595 MHz
Channel 45 is 26.605 MHz
..10 kHz spacing up to
Channel 76 is 26.915 MHz
Channel 77 is 26.925 MHz
Channel 78 is 26.935 MHz
Channel 79 is 26.945 MHz
Channel 80 is 26.955 MHz

German regulations specify:

27.025 MHz - Channel 6 - data channel - digital modes permitted
27.035 MHz - Channel 7 - data channel - digital modes permitted
27.085 MHz - Channel 11 - Internet gateways (remote stations) allowed
27.255 MHz - Channel 23 - data channel - digital modes permitted - FT8 very popular on 27.255 MHz USB
27.235 MHz - Channel 24 - data channel - digital modes permitted - ROS very popular
27.245 MHz - Channel 25 - data channel - digital modes permitted - ROS very popular
27.295 MHz - Channel 29 - Internet gateways (remote stations) allowed
27.395 MHz - Channel 39 - Internet gateways (remote stations) allowed
27.405 MHz - Channel 40 - data channel - digital modes permitted
26.675 MHz - Channel 52 - data channel - digital modes permitted
26.685 MHz - Channel 53 - data channel - digital modes permitted
26.755 MHz - Channel 60 - Internet gateways (remote stations) allowed
26.765 MHz - Channel 61 - Internet gateways (remote stations) allowed
26.865 MHz - Channel 71 - Internet gateways (remote stations) allowed
26.915 MHz - Channel 76 - data channel - digital modes permitted
26.925 MHz - Channel 77 - data channel - digital modes permitted
26.955 MHz - Channel 80 - Internet gateways (remote stations) allowed

Voice communications (AM, FM, SSB on channels 1-40, FM only on channels 41-80) is allowed on all 80 channels.  Internet gateways frequently use CTCSS (PL) tone squelch to avoid keying the remote receiver up constantly.  67.0 Hz, 77.0 Hz, 88.5 Hz and 100.0 Hz are all popular. 

In regards to out of band use (freebanding) - 27.700 MHz USB is the unofficial SSTV frequency. 

The 25.6 MHz to 26.96 MHz ("low channels") and the 27.41 MHz to 28.0 MHz ("high channels") are extremely popular with out of band CB radio users, business users, truckers, all sorts of folks.

The most popular ones are within the "low band" (directly below channel 1) and "high band" (above channel 40).

Specifically:

26.515 MHz - 26.955 MHz
and
27.415 MHz - 27.855 MHz

Note that the German 80 channel CB allocation overlaps most of 26.515 - 26.955. 

Numerous other countries have additional channels.  Good examples include:

Brazil - 80 channels, 26.965 MHz to 27.855 MHz

Russia - 240 channels (two sets of 120 channels)

Alphanumeric channel identification.  Band (letter), two digit channel number, plus the "grid" or "raster" (E for the standard band plan, frequencies end in 5, P or R for the Polish band plan, channels -5 kHz, channel frequencies end in 0).  So even though the 10 kHz spacing is in place for each of the two "rasters", the Russian CB allocation is effectively 5 kHz spacing. 

26.060 MHz to 26.500 MHz - Band A - Raster R / P (zeros)
26.065 MHz to 26.505 MHz - Band A - Raster E (fives)
26.510 MHz to 26.950 MHz - Band B - Raster R / P (zeros)
26.515 MHz to 26.955 MHz - Band B - Raster E (fives)
26.960 MHz to 27.400 MHz - Band C - Raster R / P (zeros)
26.965 MHz to 27.405 MHz - Band C - Raster E (fives)
27.410 MHz to 27.850 MHz - Band D - Raster R / P (zeros)
27.415 MHz to 27.855 MHz - Band D - Raster E (fives)

So
frequency 27.135 MHz AM would be formatted as Channel C15E AM
frequency 27.700 MHz FM would be formatted as Channel D23P FM / D23R FM
frequency 26.560 MHz FM would be formatted as Channel B05P FM / B05R FM
frequency 27.635 MHz FM would be formatted as Channel D19E FM
frequency 27.555 MHz USB would be formatted as Channel D12E USB

and so on

AM, FM, USB and LSB are all allowed.  Use of the skipped "A" channels is also widespread...that includes the skipped "A" channels -5 kHz. 

Of course, there are other examples:

UK CB radio channels - 40 + 40

the standard European 40 channel allocation (identical to the American CB band plan) is permitted in the UK.  AM, FM and SSB are all permitted on the standard 26.965 MHz - 27.405 MHz EU/CE/CEPT/US FCC band.  The UK also has an additional 40 channels UK-specific UK FM "27/81 CB" (narrow FM voice only)

27.60125 MHz to 27.99125 MHz (straight 10 kHz sequence, no skipped channels, channels are not out of order for channels 23, 24 and 25). 

The UK specifically adopted the weirdo 1.25 kHz offset (or 3.75 kHz offset, depending on how you look at it) as an attempt to cut down both interference from distant skip signals and to reduce RFI / TVI concerns.  The original UK FM rigs all had a -10dB switch to reduce RF output power from 4 watts (maximum power) to 0.4 watt / 400mW. 

The UK FM CB band overlaps with about half the "high channels" (27.415 MHz - 27.855 MHz). 

In addition to the UK FM allocation, Ireland has a service specifically for parish radio broadcasting that uses the same spectrum.  It actually has 3 channel sets for a total of 120 available channels.  FM and AM are both allowed:

CB01 - CB40 channels are, as you'd expect, CB radio channels 1 to 40 - 26.965 MHz - 27.405 MHz (AM or FM allowed)

LW01 - LW40 channels are identical to the UK FM CB band plan, with the last two digits cut off.  So instead of 27.78125 MHz, its just 27.781 MHz. 

LW01 - 27.601 MHz
LW02 - 27.611 MHz
LW03 - 27.621 MHz
LW04 - 27.631 MHz
LW05 - 27.641 MHz
LW06 - 27.651 MHz

10 kHz spacing, and so on up to

LW35 - 27.941 MHz
LW36 - 27.951 MHz
LW37 - 27.961 MHz
LW38 - 27.971 MHz
LW39 - 27.981 MHz
LW40 - 27.991 MHz

and finally the UW01 - UW40 channels:

UW01 - 27.605 MHz
UW02 - 27.615 MHz
UW03 - 27.625 MHz
UW04 - 27.635 MHz
UW05 - 27.645 MHz
UW06 - 27.655 MHz

10 kHz spacing up to

UW35 - 27.945 MHz
UW36 - 27.955 MHz
UW37 - 27.965 MHz
UW38 - 27.975 MHz
UW39 - 27.985 MHz
UW40 - 27.995 MHz

FM and AM modes are allowed on CB01 - CB40, LW01 - LW40 and UW01 - UW40.  The LW and UW frequencies are so close to each other that interference is pretty much a given if two transmitters are close enough to each other.  The vast majority of Irish 27 MHz parish radio/church radio systems use FM mode.  Just like with the UK FM allocation, there are no skipped channels, and channels 23, 24 and 25 are not out of order. 

U.S. East Coast, various HF/VHF/UHF radios/transceivers/scanners/receivers - land mobile system operator - focus on VHF/UHF and 11m

 

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