# Launch Control and PA system

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#### amarillo_rocket

##### Well-Known Member
We had an old wireless system that started having issues 5-6 years ago. I made a new wireless system 3 years ago from inexpensive wireless controllers. The system worked OK then began to become unreliable last year. Last fall I started building a system that should last for many years. The new wireless controllers are from National Control Devices. The controllers are not inexpensive but so far have performed flawlessly. Occasionally there is a need for a PA system when we have a large turnout. We put together a 40 Watt stereo amplifier kit and dynamic microphone controller kit from Cana Kit to be used as the PA system. We are almost finished with the project needs paint and the audio controller boards mounted. The design goal was something compact yet useful. The PA system also needed to be separate from the launch controller.

#### Handeman

##### Well-Known Member
TRF Supporter
Interesting. Our PA system consists of a PA amp and two large speakers on stands. I have know idea how old they are, but I've been launching with the group for 15 years and they've been there there whole time. We did replace the audio plugs on the speaker wires and get a new mic cable a few years back. It is a amazingly durable system, but nothing near as compact as what you are putting together.

Will you be able to plug in remote speakers to your system?

Have you considered the FM transmitters for audio systems? We looked into getting one so we could let the folks too far away to hear the speakers to get the PA over their FM car radios. No license required if they are below a certain wattage, IIRC.

#### ksaves2

There's these: https://www.ebay.com/itm/7W-Stereo-...nsmitter-CZH-7C-Antenna-US-Sotck/122399940808
Illegal as heck due to 7 watt output but if kept at 1 watt and steer clear of any commercial station could get away with it out in the boondocks.
Might be able to get away with it out on the playa since that ground sucks up ground level Rf like a sponge.
Don't come crying to me if the FCC slaps you with a $10k fine though. YMMV Kurt #### JimJarvis50 ##### Well-Known Member Hey Barre', how's it going! I need to come visit some day. I put together a very low tech system 3 years ago and it's worked pretty well for us. It's basically a car radio in a box. We used to have a MobileBlackBox transmitter, with I had attenuated to keep the power down. It burned out, and we replaced it with a lower power MobileBlackBox, which isn't very good. It works, but I may have to replace it per Kurt. If I had a bit more range, I'd build a couple more satellites. Jim #### amarillo_rocket ##### Well-Known Member No plan for external speakers right now but something that could easily be done in the future if needed. I could add a 100 watt amp to drive external speakers if what I have designed is not loud enough. My main goal was convenience. We had a bulky PA system we never used. We have a launch in a week so that will be the first test. #### amarillo_rocket ##### Well-Known Member Jim come on up whenever you can just check with me regarding the weather. This year rain and wind have been an issue for every launch we scheduled. So far our next launch looks OK. #### JimJarvis50 ##### Well-Known Member Jim come on up whenever you can just check with me regarding the weather. This year rain and wind have been an issue for every launch we scheduled. So far our next launch looks OK. I was looking over your schedule pretty closely end of last year and earlier this spring. Had a flight to 15K and, unfortunately, many options to that altitude have gone away. I ended up going to Argonia in February. Your weeks had lots of wind as I recall. But I'll get there. Jim #### ksaves2 ##### Lifetime Supporter TRF Lifetime Supporter Hey Barre', how's it going! I need to come visit some day. I put together a very low tech system 3 years ago and it's worked pretty well for us. It's basically a car radio in a box. We used to have a MobileBlackBox transmitter, with I had attenuated to keep the power down. It burned out, and we replaced it with a lower power MobileBlackBox, which isn't very good. It works, but I may have to replace it per Kurt. If I had a bit more range, I'd build a couple more satellites. Jim Yeah, If local coverage is an issue as far as wireless is concerned, I'd be careful with the ebay transmitters on the FM broadcast band. PO a local for messing with their farm reports (heck they ought to be listening on AM anyways!) and like I said, could end up with a$10k fine.

If one treats it like we did with "Easy Access" motors before the lawsuit was settled, can likely fly under the radar with precautions. I'd suggest turning the power down to 1 watt or less. Use a vertical dipole low to the ground or place it horizontally to change it to horizontal polarity. Up close, receivers/intended audience might be able to hear the signal. Test it out.

Have someone drive around one's intended launch site and see if the signal is too strong on the fringes of the launchsite.
I do find it nice to be able to monitor launch control while out in the field doing a recovery with a transistor radio. Can tip me when to look back if there is a cool rocket that's going to be launched.
Above all, steer clear of an actively broadcasting licensed station. With the PLL crystal controlled transmitters out there, it's easy to lock the frequency in avoiding bleeding over or into a duly licensed broadcast station. Remember, out in farmland some
of the occupants of the land might have their FM antennas up on old defunct windmill towers and their ability to pickup your signal is greatly enhanced even if you are using low power. If you aren't interfering with a station they are interested in listening to, they'll more likely keep tuning on to something else. Lord knows it would be very easy to identify who is the source of launch banter so be careful.
The farther out in the boondocks one is with no people living nearby, the more one could get away with without bothering anyone. As mentioned out in the playa with the Rf attenuation salts in the ground and the isolation
from civilization, can likely have more leeway and remain unmolested. Again, YMMV. Kurt

#### JimJarvis50

##### Well-Known Member
When we were running the higher-power system, I had an attenuator on the antenna and we put it on the ground. I don't think the signal got out of the immediate launch area. A drawback of FM though. Barre', how does your wireless system work?

Jim

#### amarillo_rocket

##### Well-Known Member
The completed controller and PA system. The volume is surprisingly loud and much better than having to yell as we have done in the past. I found having the microphone pre-amp at full output delivers the cleanest sound to the power amplifier.