Dsm vs 75

[Tom Foley]

Okay guys, I've tried to stay out of this thread, but I feel like it's time to try to sort this one out. Let's start with Al Water's post:
With the advancement in radios over the past few years and more specifically the development of the DSM
Frequencies, the need for the older surface frequencies has all but disappeared. While there are a few
individuals still running these frequencies, the overwhelming majority has switched to DSM. The purpose of
this proposal is to encourage the retirement of these frequencies to eliminate the need for transmitter
impounds and frequency coordination in composing heats.
The intent of this rule is to limit the frequencies offered at NAMBA sanctioned events to just the DSM band
after 2023. The older 27Mhz, 50Mhz and 75Mhz frequencies will still be available for sport boating or for nonsanctioned NAMBA races.
I see a couple of things that are very important for us, as boaters, in his post:

1. advancement in radios over the past few years and the development of the DSM Frequencies
2. the overwhelming majority has switched to DSM
3. eliminate the need for transmitter impounds and frequency coordination in composing heats.

With these three things extracted from Al's post, let's look at the "why" behind them:

• Since the DSM became a reliable system, they have been more and more what has been available to the modeling community, pretty much phasing out the older types of protocols and frequencies in much the same way the automatic transmission has replaced the manual in almost all vehicles, other than the heavy-duty ones. Even some semi tractors are equipped with them to make the driver's work load easier.
• Why has the "overwhelming majority" bought DSM systems? They aren't any cheaper than a 27, 50 or 75MHz system so it's not the cost. I bought my 4PLS since I didn't see a wheel radio on any other band than 2.4GHz being offered by Futaba. It also had features that aren't on my 9CAP, such as servo speed controls. Does that give an indication as to where the market is pushing us?
• transmitter impounds and frequency coordination are just a benefit to those running a race. By not having to worry about them, it streamlines operations. If two people still want to pit for each other, they can still say they are on the same non-DSM frequency and run as they always have.

One thing Al didn't have in his post is SAFETY. Safety is an issue that, for the most part, DSMs have improved. We no longer have to have a frequency pin to turn on our radios since the receivers only respond to the "linked" transmitter. This eliminates the chance of a runaway due to someone else overriding the boat owner's transmitter signal. Obviously, a radio part failure will still cause a boat to go out of control but, all things being equal, it was the same way with the older, non-DSM systems.

We definitely need to look at banning OPS 67 , Picco 67., MAC 67 since the CMB drum intake engines are much better and more modern .

 

[Norm Doerr]

We definitely need to look at banning OPS 67 , Picco 67., MAC 67 since the CMB drum intake engines are much better and more modern .

No carbs must be injected.

 

[DON MAHER]

The current total number of entries listed on RC events as of this moment is 1,516, of that number 37 are on the 27-75 band ! This is just a bad rule! JMO

 

[DougSick]

In the mid 90's I tried to run 75mhz on a couple of boats. I went to a Nats where there were a lot of 75 mhz and had no end of problems with interference. My boat ran fine until certain people fired up their radio and the boat went nuts. I took two radios with different channels into a shop that had a frequency analyzer and found that both were fine on their own but when both were on, two more frequencies showed up at half strength on adjacent legal frequencies on either side of the two that were on. That turned out to the problem with 75mhz and the way frequencies interacted. I switched back to 27mhz, which by then, had been deserted for the most part and had little issue with competing boats. I had to give up on 27mhz as I could no longer get LCD screens for the raidos I had. Great radios other than that.
The only issue I can say that I've had with DSM was one, a broken tip on the coax antenna which was caused by repeated bending where it exited the antenna tube, and two, in Europe where two of us from Canada had receivers freeze at a particular point on the lake. The locals had no problems like us and it came down to the fact they used antennas that were 6 inches longer. We replaced the antennas at the race and had no problems after that. There were a number of large radio towers in the area so we figured there must have been an interference that only occurred at that point in the lake if our receiver antenna did not have proper distancing from the tuned pipe. I have since converted all receivers to longer antennas that put the tip at least 4 inches clear of the pipe. I also keep the tip inside the antenna tube so it does not get bent. I have seen a lot of folks bend the end over and put the cap on which I think will break the antenna in the long run. Overall, I can't say enough about proper antenna set up and I shake my head at folks that just lay a short antenna in the radio box. Maybe they just get lucky.
Some time back I had read of complaints that some folks were entering using the same frequency so they were not placed in the same heats, in spite of actually running DSM. I guess there was no rule against it or at least they had influence with the CD and the practice was allowed. Not sure if this is what prompted NAMBA to make the change but I agree with it as it is bringing the superior DSM technology into play. DSM radios can be bought for very reasonable prices and they have way more programming that I ever need.

 

[Tom Foley]

In the mid 90's I tried to run 75mhz on a couple of boats. I went to a Nats where there were a lot of 75 mhz and had no end of problems with interference. My boat ran fine until certain people fired up their radio and the boat went nuts. I took two radios with different channels into a shop that had a frequency analyzer and found that both were fine on their own but when both were on, two more frequencies showed up at half strength on adjacent legal frequencies on either side of the two that were on. That turned out to the problem with 75mhz and the way frequencies interacted. I switched back to 27mhz, which by then, had been deserted for the most part and had little issue with competing boats. I had to give up on 27mhz as I could no longer get LCD screens for the raidos I had. Great radios other than that.
The only issue I can say that I've had with DSM was one, a broken tip on the coax antenna which was caused by repeated bending where it exited the antenna tube, and two, in Europe where two of us from Canada had receivers freeze at a particular point on the lake. The locals had no problems like us and it came down to the fact they used antennas that were 6 inches longer. We replaced the antennas at the race and had no problems after that. There were a number of large radio towers in the area so we figured there must have been an interference that only occurred at that point in the lake if our receiver antenna did not have proper distancing from the tuned pipe. I have since converted all receivers to longer antennas that put the tip at least 4 inches clear of the pipe. I also keep the tip inside the antenna tube so it does not get bent. I have seen a lot of folks bend the end over and put the cap on which I think will break the antenna in the long run. Overall, I can't say enough about proper antenna set up and I shake my head at folks that just lay a short antenna in the radio box. Maybe they just get lucky.
Some time back I had read of complaints that some folks were entering using the same frequency so they were not placed in the same heats, in spite of actually running DSM. I guess there was no rule against it or at least they had influence with the CD and the practice was allowed. Not sure if this is what prompted NAMBA to make the change but I agree with it as it is bringing the superior DSM technology into play. DSM radios can be bought for very reasonable prices and they have way more programming that I ever need.

Through the 90's till present I have run 5-7 different classes at races.with over 300 boats , mine all on channels 88 and 90 , controlled impound and uncontrolled and never had a radio problem using the 1024.PCM recievers with the 3 - PB and 3 - PK without any radio issues that were not switch or battery related . It's a reliable system and no one .......No One can dispute that fact honestly. I have made the switch so I can race at NAMBA events and time will tell if I have any issues .

 

[Mike Hughes]

Through the 90's till present I have run 5-7 different classes at races.with over 300 boats , mine all on channels 88 and 90 , controlled impound and uncontrolled and never had a radio problem using the 1024.PCM recievers with the 3 - PB and 3 - PK without any radio issues that were not switch or battery related . It's a reliable system and no one .......No One can dispute that fact honestly. I have made the switch so I can race at NAMBA events and time will tell if I have any issues .

Always loved the square wave signal of the PCM system. Nothing talked to it but itself.
Mike

 

[John Beardslee]

One of the things that hasn’t been mentioned yet about 27, 72 & 75 mhz is their susceptiblity to mechanical noise. Everything from push rods rattling to bearings in the struts vibrating could and did cause glitches. I made the change to DSM immediately while flying heli’s. It’s almost totally immune to noise but it is a line of sight signal so you are advised to not walk behind a building or let anything get between your transmitter and receiver. In Europe there are places that you can’t use DSM (or at least there was) because the military radar (NEXRAD) sp? dithered there signal enough to interfere with DSM. The early days of DSM coincided with the transition to digital servos that had considerable more current draw than the analog servos and many issues blamed on DSM were actually brown outs caused by servo load or the low voltage threshold in the receivers not being paired to the new servos. DSM is quicker, not so noticeable in a boat but big time in a heli or carpet cars.