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UHF RC system version 3 booster 7W V4.00 Latest New Version

Booster V3.10 Old version
Booster V3.33 Old version
Booster V4.00 PRO version NEW
see also 30W PA stage for ultra long range
see also old version 2, we have test flown V2 for over 1yrs now
see also version 3 rc system

Here is the NEW PA Booster version 4 with improved and bigger heatsink, and a few new features

NEW FEATURES of V4: added safety and security
Auto power on from 50mW input it will power up
if no RF signal input it will idle at zero current, so it can now be left powered on all day long
LED indicator one dual color, red-green
Green lit constantly = all is perfect, RF level in is fine, and DC supply is fine
Green off blinks start at 150mW and down to 50mW, longer and longer off time = less input power
Red blinks show input voltage is under 6.8V
longer and longer RED lit time when voltage drops more.
Green and Red blinks can be active at the same time in case both low rf level and low voltage
booster still works at different voltages, and can now be powered as low as 2-3V

The booster will give good power from 125mW to 500mW input
500mW is nominal input, 125mW is -6dB accepted max cable loss, at this point output will drop 1db
input will survive 1W for 10 sec, and 2W for 2 sec, maybe more but I did not dare to test the kill time

The previous booster versions had idle currents in the 400-600mA range, so booster could not be left powered on when not flying
risk of using all battery power existed. Users with V3.x boosters must be aware of this.
Idle current is defined as the current the booster draw with no RF input

Idle current for booster V4 is only 1.4 mA !

This tiny PA booster is designed to get 500mW input from the V3 RC system
Boosting 0.5W to 7W will increase the range by at least a factor 3 !
The PA module consume about 2A at 7.2V and give 7 to 8 Watt out of pure long distance RF power

I use a big heatsink so it can be opperated 24hr if needed.
The PA booster box is a small metal case 58mm wide, 72 mm long, 27 mm height

Inside the booster version 4. note the end plate connector PCB's

this extra PCB makes it faster to assemble, and lower loss.
The new booster have a little bit better specifications.

Booster Specifications Version 4 at 500mW input
Vin, Current in, RF Power Out, Efficiency:
9.0V 2.58A       9.12W         39%  DO NOT GIVE UNIT OVER 8V
8.5V 2.50A       8.71W         41%  DO NOT GIVE UNIT OVER 8V
8.0V 2.42A       8.51W         44%  MAX recommended supply voltage
7.5V 2.32A       7.94W         45%  
7.0V 2.22A       6.92W         44%
6.5V 2.12A       5.89W         43%
6.0V 2.00A       4.00W         33%
5.5V 1.90A       2.95W         28%
5.0V 1.78A       1.74W         19%
4.5V 1.67A       1.35W         18%
4.0V 1.55A       1.12W         18%
3.5V 1.40A       851mW          
3.0V 1.03A       589mW          
2.5V 613mA       245mW
2.0V 180mA       11mW
So it is possible to change RF power by simply using powersupply voltage adjust.
a 6 cell NIMH battery and a rotary switch (brake before make) can be used.

RF cable
The BNC - BNC cable you need to use from standard 500mW tx unit to your booster (is not supplied)
use any 50 ohm impedance cable with loss from 0dB to 6dB at 500MHz.
network cables with BNC 10base-2 are 50 ohm, cheap and available world wide.
Different cable types have different loss, here is the max length allowed using different cables:
RG-58CU 18meters (59ft)
RG-223 17meters (55ft)
RG213U 37meters (121ft)
Ecoflex10 67meters (219ft)

install and use
It is recommended to place this booster with antenna as far away from ground station video receivers
as needed, to achive full video range ! this must be checked with booster on/off.
mount booster with antenna as hight and free as possible to achive as good range as possible.
Directional antennas will give you futher range, a gain of 10dB = 3 x the range !
ham radio beam antennas for the 70cm band are cheap and easy to get worldwide.

old 3xx rx firmware:
The ultra sensitive receiver will be blocked/jammed if distance to booster antenna is under 10-20meters so avoid that !
no permanent harm to the receiver, only RC lock up -> failsafe, but can be harmfull to plane !
With no booster (500mW standard) avoid distance to receiver under 2-3 meters !

NEW 307-308 or higher RX firmware:
No more blocking problems, an RX can be as close as 25cm (10 inch) from a booster at 7W before minor blocking is detected.

Temperature Check your booster is not running too hot, a heatsink temperature of 50C (122F) is maximum allowed !
50C is arround that temperature it is impossible to touch the heatsink for 3sec !

Power supply MAX is 8.4V, max supply current 2.5A, newer ever exceed that.
Use 6 cell NIMH battery or 2 series LIPO cell.
Do NOT reverse voltage polarity, a fuse inside the Booster wil blow if reversed and if lucky the amplifier is possible to repair cheap
Do NOT opperate this PA without output antenna connected.

High / low power
see on the supply voltage chart you can use supply voltage to adjust the watt out,
and then also the range, the idea is to use as little as possible power, seek far away, looking for range problems,
when you get problems you can switch up the power and continue your mission or return home safely.

here the normal 8V supply from 2S lipo, and via the switch 3.6V will give you 1W

This is a more safe way to do it, you can change lo / hi on the switch.
And, when lipo is empty the nimh pack will save your plane.
you can use other cell counts to fit your needs, for the low power section, maybe use 4 or even 5 NIMH cells
sorry about the ugly pictures, they where made in 15 sec :-)

-Thomas Scherrer OZ2CPU (active with this from 2006-2009) this page was last updated December 1, 2009