Which Lectrosonics blocks are still legal in the US?

Blocks A1, 19, 20, 21, B1, 22 and 23 sit entirely within 470–608 MHz and are legal nationwide. Block 24 is legal only across 614.1–616 MHz and block 25 only across 653–663 MHz, while blocks 26, 27 and 29 have no legal US operating range at all.

What frequencies does Lectrosonics block 21 cover?

Block 21 covers 537.600–563.100 MHz, the same span as the block labelled B1. It falls entirely inside the legal US UHF band of 470–608 MHz, so it is usable in any market subject to local TV occupancy.

Can Lectrosonics block 24 still be used?

Only barely. Block 24 spans 614.100–639.600 MHz, and just the bottom portion up to 616 MHz falls in the legal 614–616 MHz guard band at 20 mW EIRP. Everything from 617 MHz up is 600 MHz service band spectrum and prohibited.

How wide is a Lectrosonics block?

Most blocks are about 25.5 MHz wide. Block 23 is the exception at 19.1 MHz (588.800–607.900 MHz), because it is cut short so it never reaches TV channel 37 at 608 MHz.

What is Lectrosonics block 941?

Block 941 covers 941.000–960.000 MHz, which overlaps the licensed Part 74 allocation at 941.5–959.85 MHz. It is not an unlicensed band, so it is only lawful for operators who hold a Part 74 low power auxiliary license.

Gear & blocks

Lectrosonics blocks: what each one covers

RF ScoutUpdated July 26, 20264 min read

Lectrosonics divides UHF into roughly 25.5 MHz blocks. Blocks A1 (470.100–495.600 MHz), 19, 20, 21/B1, 22 and 23 sit entirely inside the legal US band of 470–608 MHz and work anywhere in the country. Block 24 (614.100–639.600 MHz) is legal only across its bottom sliver of 614.1–616 MHz, block 25 (640.100–665.600 MHz) only across 653–663 MHz, and blocks 26, 27 and 29 fall wholly inside spectrum auctioned to mobile carriers — they cannot legally transmit in the United States at all. Block 941 covers 941.000–960.000 MHz and is licensed Part 74 territory only.

Lectrosonics splits UHF into numbered blocks about 25.5 MHz wide, which is narrow enough that the block you own decides where you can work. Half the catalog predates the 600 MHz auction, so a transmitter can be in perfect condition, fully supported, and still tuned into spectrum that belongs to a mobile carrier. Here is every block in the RF Scout catalog with its exact edges and its legal status today.

The block table

Ranges are the inclusive tuning extents of the block. The legal-portion column reflects US rules only — see what frequencies wireless mics can use for the underlying allocations.

Lectrosonics blocks and their US legal status
Block	Range (MHz)	Legal US portion	Status
A1	470.100–495.600	All of it	Fully usable
19	497.600–523.100	All of it	Fully usable
20	512.000–537.500	All of it	Fully usable
21	537.600–563.100	All of it	Fully usable
B1	537.600–563.100	All of it	Fully usable (same span as 21)
22	563.200–588.700	All of it	Fully usable
23	588.800–607.900	All of it	Fully usable — stops below ch. 37
24	614.100–639.600	`614.1–616 MHz` only	Mostly illegal — 617+ is carrier spectrum
25	640.100–665.600	`653–663 MHz` only	Mostly illegal — duplex gap sliver only
26	665.600–691.100	None	Illegal in the US
27	691.200–716.700	None	Illegal in the US
29	784.000–805.000	None	Illegal in the US
941	941.000–960.000	`941.5–959.85 MHz`	Licensed only (Part 74)

How the numbering works

The numbered blocks step upward in 25.5 MHz increments, which is why 19 through 23 line up neatly and then stop. Block 23 is the odd one out at 588.800–607.900 MHz — only 19.1 MHz wide, because it is deliberately truncated below 608 MHz so it never lands in TV channel 37. That truncation is the single clearest sign of where the legal ceiling sits.

A1 and B1 are letter aliases, not extra spectrum. A1 covers 470.100–495.600 MHz; B1 covers 537.600–563.100 MHz, the identical span to block 21.
Blocks overlap on purpose. Block 19 ends at 523.100 and block 20 starts at 512.000, so a two-block kit built from 19 and 20 buys less unique spectrum than the numbers suggest.
Above block 23, coverage gets thin fast. Block 24 contributes under 2 MHz of legal tuning and block 25 about 10 MHz, split across a licensed-only half and an unlicensed-only half.
Block 941 is a different animal. 941.000–960.000 MHz is Part 74 licensed spectrum, not a UHF block, and it is only legal for operators who actually hold the license. See do you need an FCC license.

Building coverage out of 25.5 MHz slices

A single block is a bet that one 25.5 MHz window will be clear wherever the job takes you. In a light market that bet usually pays. In a dense one, a full-power station or two inside your only block can leave you fighting for four channels where you needed eight. Two blocks that do not overlap — say one down near 470–500 MHz and one up around 563–589 MHz — is a far more durable position than one block plus hope.

The blocks that are entirely inside 470–608 MHz are the ones worth building around, because they are legal in every US market without qualification. Everything from block 24 up is a fragment at best. If a rental package or a used deal is priced attractively, check which side of 608 MHz it lives on first.

Buying used

The used market is full of blocks 24 through 29 at prices that look like bargains, for the obvious reason. A block 26 transmitter has no legal domestic use. A block 24 or 25 unit has a legal use so narrow it is hard to coordinate around — and in block 25, 653–657 MHz requires a Part 74 license while 657–663 MHz is unlicensed-only, so half the window is closed to you either way.

Once the block question is settled, the remaining work is local: which TV channels inside your block are occupied at the address you are shooting. That varies by mile, not by state — see why wireless drops out near TV towers and scanning and walk testing.

Enter an address and see which of your Lectrosonics blocks have room at that spot.

Check your blocks against a location

Common questions

Which Lectrosonics blocks are still legal in the US?: Blocks A1, 19, 20, 21, B1, 22 and 23 sit entirely within 470–608 MHz and are legal nationwide. Block 24 is legal only across 614.1–616 MHz and block 25 only across 653–663 MHz, while blocks 26, 27 and 29 have no legal US operating range at all.
What frequencies does Lectrosonics block 21 cover?: Block 21 covers 537.600–563.100 MHz, the same span as the block labelled B1. It falls entirely inside the legal US UHF band of 470–608 MHz, so it is usable in any market subject to local TV occupancy.
Can Lectrosonics block 24 still be used?: Only barely. Block 24 spans 614.100–639.600 MHz, and just the bottom portion up to 616 MHz falls in the legal 614–616 MHz guard band at 20 mW EIRP. Everything from 617 MHz up is 600 MHz service band spectrum and prohibited.
How wide is a Lectrosonics block?: Most blocks are about 25.5 MHz wide. Block 23 is the exception at 19.1 MHz (588.800–607.900 MHz), because it is cut short so it never reaches TV channel 37 at 608 MHz.
What is Lectrosonics block 941?: Block 941 covers 941.000–960.000 MHz, which overlaps the licensed Part 74 allocation at 941.5–959.85 MHz. It is not an unlicensed band, so it is only lawful for operators who hold a Part 74 low power auxiliary license.

Sources

Related notes

Field Notes are general reference, not legal advice or a substitute for the rule text. Spectrum rules change; verify anything you are relying on against the current source before you transmit. See the methodology and disclaimer.