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With the expanding popularity of DIY building of ground based FPV models (or so called ground drone) on platform such as trucks, cars, crawlers, off-roader and on-roader the demand for long range radio started to surge up in the community that lust for longer distance driving.  In order to achieve long range ground driving distance equal to the minimum distance achieved by air base platform such as fixed wing and multirotor which can travel at minimum between 1.5km~2km the radio controller unit must use ideal long range radio frequency and protocol that could perform such task.  Usually most radio controller would use classic frequency such as FM modulated 42~72 Mhz or todays 433Mhz, 800Mhz,  900Mhz or non-telemetry (low latency one direction) 2.4ghz which usually available as 'detacheable module' that can be attached and detached from the back of the radio unit popularly used on air stick controller.  Which is why many 'long range' pilot or driver would use air based stick controller if they want to travel long distance on FPV activities.  Unfortunately today radio unit comes stock/default as high latency 2.4Ghz for performance flight and driving optimized for fast response, telemetry feed back features and become part of radio integrated circuit to make it light and compact on user hand.  This 2.4Ghz feature is common on 'Pistol Grip' radio (the one with round steering wheel) which is built for ground R/C models such as for  cars, trucks, off-roader and on-road models which demand fast and precision control especially during racing.  However this fast responding frequency uses short wavelength to store compact data/information for speed at short distance rather than longer wavelength as seen on audible radio station that you heard on your car or home radio. So 'high response' 2.4Ghz is not ideal for long range FPV.  Unfortunately by the year 2020 all ground 'Pistol Grip' radio comes with integrated 2.4Ghz which cannot be change unlike 10 years back where radio transmitter module was removable, only air radio controller/stick radio retain this feature.

Why not recommended to use 'Air based Radio' to drive?

Air based radio or known as stick radio is widely used to control planes, helicopters, multirotors or any air borne models.  However many ground FPV'er use them to drive their trucks, cars and other ground platform for long ranges because this radio is the only controller that could support detachable radio module that user can manually switch to better radio frequency as mention before such as FM frequency, 433mhz, 800mhz or 900mhz for better radio penetration through ground obstacles....you can watch few ground FPV enthusiast drive around long distance on their truck models on Youtube video.  Another plus when using these 'Air radio' controller is it can support head tracking via trainer/PPM input port which is a lacking feature on normal 'Pistol Grip' controller which only have 'DSC' (Direct Servo Controller) output signal only.

Unfortunately the drawback when using the air based controller (Stick Controller) is that the throttle stick doesn't have any throttle return spring to center the throttle throw since ground based model 'ESC' run on 'Forward > Brake > Stop > Reverse' command at 100%-0%-100% stick throw rather than 0%-100% linear throttle for planes, helicopter and multirotors.  This makes it hard to drive since you'll need to manually move the stick to neutral position to stop without over reversing it....this happens a lot to my wingman buddy who drive behind me and keep hitting the back of my truck as he was confuse how to stop on a thumb stick since there's no neutral point to stop as seen on my FPV driving Youtube video in the past. This also makes it worse when you try to calibrate a car/truck ESC unit. Some radio stick have self DIY to make the throttle stick self centered while others can be a cumbersome to do it.  For FPV racing such as high speed on-road and off-roading 'Pistol Grip' radio handles better and felt more neutral especially if you're seasonal racer using such controller which is why its easy for me to speed around the circuit on my RADIOLINK RC4G pistol grip controller.      Back in the 80's stick controller for R/C cars and trucks was a common scene up till early year 2000 such as the popular FUTABA ATTACK, unfortunately that era was long gone.

Alternative source for 'Pistol Grip' radio for FPV

The best 'Pistol Grip' radio for FPV is the one that have removable radio module just like the air radio, however this radio exist during pre-2.4ghz era when 2.4Ghz was consider a luxury feature on higher end radio while other intermediate enthusiast was still running on stock AM 27Mhz up to FM 42~72Mhz which pre-dates between year 2000 up to 2010.  Back in the days higher end radio has removable radio module which they can swap around their radio frequency protocol back and forth from AM, FM to 2.4Ghz.   The most important feature we want from this radio is to acquire the PPM signal pulse pinout so that we could connect to any choices of long range capable radio module to the controller without being stuck with just one radio protocol which has default short range.  I have an old radio the SANWA M-11 that has removable radio module which is a good news...unfortunately it was a heavy radio control unit to hold on for hours. If you're interested to know which radio has detachable radio module below are the list of radio i knew back then exist but you'll need to dig deep into second hand market since these almost obsolete or extinct in the hobby community:

• SANWA M8 or AIRTRONICS M8
• SANWA M-11 or AIRTRONICS M-11 (not M-11X)
• FUTABA 3PK
• KO-PROPO EX-10 HELIOS
• FLYSKY GT3 *classic radio only. (not the GT3B or GT3C)

Other than above there a lots of classic 'Pistol Grip' radio that have removable module exist in the market but the listed above are the ones i could remember. Good luck finding one today in the year 2020, lol!  If you're out of luck finding one then let me introduce a radio that rise from the garbage dump!  The SANWA/AIRTRONICS MX-A!!...

Step by step modification of the MX-A radio

• Converting SANWA MX-A (AIRTRONICS MX-A) for external radio module via PPM pinout port

Fortunately if you're in the budget looking for a quick and cheap way to obtain 'Pistol Grip' radio that capable to use external radio module for long range FPV then you're in luck.  I found this long lost art of modding an old radio unit that was commonly used back in the days when RTR models was on radio AM frequency on crystal slot. Meet the year 2004 radio model the 'SANWA MX-A' or known as (AIRTRONICS MX-A in the west)  radio; this AM frequency radio was a common scene decades ago before 2.4Ghz radio was born. The disadvantages of MX-A back in the old days was there used to be lots crashes and runaways due to conflicting radio bands where same frequency crashing each other because frequency hopping doesn't exist in those era....R/C hobby was a struggle back then, lol.  To be honest if it wasn't on AM 27Mhz frequency this radio performed better, lots of tunable setting, feels good and smooth in hand compare to today intermediate radio such as today's FLYSKY GT-3B/C despite being 2004 radio unit which is almost 16 years apart. 

As for the interest of FPV use this is the only radio which i knew could use external radio module through simple modification via minor soldering works.  We just need to pull out the PPM output signal and also power supply to run and power external radio module the same principal how air radio controller using it.  To my available knowledge this is the only radio i found on the internet which previously discussed on Rcgroups.com and Rctech.net  R/C cmmunity forum on how to convert AM radio to 2.4Ghz by finding the PPM pinout on the MX-A pcb board and connect it to external CORONA 2.4Ghz transmitter module back then.  The same PPM output also can be use to use on 433Mhz, 800Mhz and 900Mhz radio transmitter module as long we power it with correct voltage into the module.   This SANWA MX-A /AIRTRONICS MX-A radio still available at any old R/C store, online Ebay or any second hand hobby store at extremely cheap price for $10 or $5 at bargain bin price or at garage sale.  Sometime you can get it for free since many R/C hobby store consider these radio as retro junk or useless which is why i got handful of them in my collections. As once said 'One's trash is another man's treasure!'.   So let cut the talk short and i'll show you step by step on how to convert this old MX-A radio capable to use external radio transmitter module.  Don't worry its super easy to do it! Lets Begin!

STEP 1:
Remove the back plastic casing of MX-A radio by unscrew all the screws from top to bottom.

STEP 2:
Once done look at the back of PCB circuit. Locate 3 essential point on the board; the PPM signal pin-out, the 12v (+) positive battery terminal pin-out and 12v ( -) grounding battery terminal pin-out.  You'll need to solder wire connection at this point.  The corresponding pin-out location can be found by clicking the picture below to enlarge:

STEP 3:
Get a 'male' servo connector or any 3 pin equivalent connector wire that able to plug to your preferred external radio transmitter module that have PPM input.  My external radio transmitter module will be a QUHF 433Mhz module that requires PPM input and 12v power source; so i'll need to solder the wire connection to the said pin-out on the board.

* Take note that some external radio module only need to power  at 5V such as eg:  FRSKY 2.4Ghz DJT module which you need to step down the power from MX-A board from 12V to 5V using voltage step down regulator or 5V/3A BEC before routing the power into the transmitter module.

STEP 4:
Drill a hole on the back of the radio controller plastic cover so that all 3 wired pin-out can routed out to external module behind the plastic casing.

STEP 5:
Re-arrange all the wirings, make sure all 3 wired pins exited out behind the panel and screw back the plastic back plate of the radio unit.

STEP 6:
Remove the AM crystal radio band from the front side of radio crystal slot. You can also remove the shiny telescopic antenna too after the AM crystal removed from the slot.

STEP 7:
Find ways to DIY attach the external radio transmitter module behind the MX-A radio...either Velcro stickies, hot glue or double sided 3M sponge tape.  Then plug in the PPM signal, V+ and V- power pin-outs into the module port.  Done!

Summary

There you go! Job done! Now you got yourself a customized cool FPV radio unit that uses hand picked long range radio transmitter module that offer have far better range than 2.4Ghz or stock AM frequency.  Else if you just wanna recycle back the use of MX-A for ordinary line of sight R/C driving you can use any 2.4Ghz radio protocol of your choice from FHSS, DSSS, AFHD series or SPEKTRUM.  The most important thing is you got yourself a cheap and effective long range FPV transmitter without burning hole in your pocket!  Enjoy!