Is 72mhz a no go?

[DrScoles]

I have been building planes forever, and use the Futaba 32mz for my jets and warbirds. I have purchased three sub kits. I'd really like to stick with a radio that is programmable. On the Engel Typhoon, it seems like a few of the electronic components could be eliminated by using mixes in the radio. I have an old 14mz with a 72mhz module. Not sure they even made a 75mhz module for this radio? My desire to get into subs was spurred by getting a vacation home with a swimming pool. I may never go to an actual event, but the idea sounds fun. I haven't seen anyone using 72mhz at a flying field in ten years, everyone is on 2.4. Would 72mhz be allowed at a sub event? Finding the antenna and a module for the 14mz was an endeavor!

Really excited to get going on these kits, but the radio has been a stumbling block.

[feet wet]

Not knowing where you are... 72mhz is only an aircraft frequency and NOT legal for use in surface, or sub-surface, craft. It may be a largely dis-used frequency range, but until the FCC changes that, you need to go with 75mhz, or even 27 mhz ranges. The later was used for CB for so long, but now may be an option.

[salmon]

To answer your question, the official SC response is we would not allow illegal frequencies at sanctioned events.

That being said, I know people that run 40MHz and 72MHz at local runs or on their own. I cannot condone it, but I can empathize for the reason of using it.

[DrScoles]

thanks, pretty much what I figured. If my subs want to venture out of my swimming ppol, I'll figure out 75mhz!

[crueby]

There used to be a couple places that would retune a 72 to 75 mhz for you, they still around?

[sam reichart]

There used to be a couple places that would retune a 72 to 75 mhz for you, they still around?

Radio South was one of them.

[Ralph --- SSBN 598]

Radio South https://radiosouthrc.com/

[DrScoles]

thanks, sent him an email....

[DrScoles]

Ok sportsfans, what about this: dual band 2.4 and 900mhz at the same time. One of my friends in Israel swears by FRSKY and he has a ton of jets on this dual system. I think the jet community here is too snobbish to use a $400 radio on their $10-15K jets.... So I haven't seen a single person here using this system.

https://www.amainhobbies.com/frsky-x20-tandem-2.4ghz-transmitter-bundle-blue-frk-03084003/p-qqqcqqqagm2zqctz

[David F]

You highlight the problem we are having with r/c equipment for subs in the US and the UK (Germany is still fine with 40Mhz) i.e LACK OF COMMERCIAL EQUIPMENT!

The supply is dominated by model aircraft users and the frequency used is going "skywards" and so is useless for us. You mention Futaba compatible 433Mhz. This WAS a solution but the equipment is no longer available from Hobbyking. The RX has been out of stock for many months.

The whole saga is related in the link below:

https://www.theassociationofmodelsubmariners.com/t83p225-uhf-radio-control-for-submarines-openlrs-lora-fsk-etc-on-458mhz-and-433mhz

The latest development is DIY equipment using basic UHF modules.
You mention that you are a Ham and so you may choose to get your soldering iron out and join us !

The situation would also be very suitable for a small, niche commercial outfit to make specialist gear at an appropriate (high?!) price.

David

[DrScoles]

david, there is a young man in Israel who is an electrical engineer who is making a ton of telemetry gadgets and other electrical devices for the jet crowd. I will share that link with him and see if he is interested. Is the 900mhz rx and tx I shared above legal here in the US? How many units do you think we're talking about?? He has a sponsorship with FRSKY, so knows their stuff well. I bought three sub kits before I even though about the radios being a bottleneck for me!!!

[David F]

Difficult questions!

I think that 900 Mhz is available in the US. (I live in the UK) You will need to search the FCC for guidance.

Regarding the market. I quote "Quartermaster" on this Forum (Thread: 2.4GHz for the RC Submariner….the next step. 07-16-2020, 06:52 PM) who puts it well in a few brief words:

"That's your opinion man....especially regarding what's NOT the way to go.

10k RC Submariners WORLDWIDE (if that, as Bob Martin who probably knows them all) is NOT a huge market.

Do you know what it cost's to lobby in this country??

100 million drone users, THAT"S a huge market.

Good luck convincing a Manufacturer to work to those numbers.

Get a guy coming into the hobby from the 2.4Ghz world of everything else and tell him to get a license, or outdated RC gear.

He'll find a new hobby,

Meanwhile, I enjoy running in anything, including salt water *. But that's MY way to go, happily painted into the corner. "

* I think that Quartermaster uses a 2.4 Ghz antenna on a float.

So I would say that subs are very much a niche market with quite conservative customers. Not exactly rich pickings!

[wlambing]

IIRC, Bob Martin did some experimenting with 900 mhz and found it to be a no-go for submarining. He had a YouTube video up about it.

[salmon]

IIRC, Bob Martin did some experimenting with 900 mhz and found it to be a no-go for submarining. He had a YouTube video up about it.

Welllllll, not completely. In a pool, even 75 MHz can have issues. Tim Senecal uses 900 MHz a lot and has tuned his setup with better antenna. It runs O.K. with limitations. It does not travel deep in water, but he can run submerged. The key is it will not be 100' offshore or 3' deep runs. He has created feedback (battery levels, direction, rpm, etc) using 900MHz. If kept closer to shore it runs fine. I believe he just ran in SF fun run.

[David F]

Well said, Salmon.

900 MHz is getting to be rather too high a frequency for water penetration. 433 Mhz performs better. 433 is a "Goldilocks frequency". High enough to carry return telemetry but low enough to penetrate water.

(This is a bit of an oversimplification because the type of modulation is another factor when using UHF frequencies. That is why using LoRa (Long Range etc. Originally suggested by Tim S) seems to work particularly well.)

I think that Tim S went to 900 MHz because he was wanting to use commercially available equipment. He felt that performance at 900 Mhz was just about OK.

If you wish to control at depths of 6 feet or so you are better off with 75 MHz (or 40 Mhz in the UK) anyway.