RediRad™Radio Adapter

This wired modulator enables you to use almost any portable audio device via the existing radio of your classic or modern car.
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Introducing the RediRad™ to the UK

I have fitted a RediRad™ to my ‘positive earth’ 1966 classic car, and I am seriously impressed now with the sound from the original Smiths Radiomobile radio, and the phone ‘hands free’ functionality is a real bonus.

  • No Modification To The Existing Radio.
  • Maintains Original Appearance.
  • A Reliable Auxiliary-Input Solution For Classic or Modern Car Radios.
  • Quick Installation.
  • Compact.
  • Solid State Construction, Made In The USA.
  • Thousands Already In Use In USA & Europe.

This is far superior to cassette-deck adapters and inferior & illegal wireless modulators.

Save hundreds compared to a radio conversion or replacement.

  • Models available are:
  • Positive Earth ‘AM’ (Medium Wave)
  • Negative Earth ‘AM’ (Medium Wave)
  • Negative Earth ‘FM’

Price is £110.00 inclusive of all shipping, import charges, VAT and ‘Royal Mail Signed For’ delivery to a UK address.

Usual cost to UK buyers buying from the manufacturer or other outlets in the US end up paying import charges, shipping and delivery and the total adds up to around £130.00 per unit.

The RediRad
RediRad installed in JAG using smartphone


Product Review: RediRad Radio Adaptor
Posted in Rover P4 Drivers Guild Forum.
Sat Sep 24, 2016 1:04 pm

The “RediRad” is a small unit intended for use with car radios, which allows you to listen to your own source of programmes or music on your set. It creates a mini medium wave (or FM) signal direct to the car antenna lead, which you then tune into in the normal way on the dial.

Separate versions that provide an AM or FM signal are available. The AM units – the ones appropriate for P4 owners – are available in positive or negative-earth versions.

I recently obtained an AM RediRad for installation with the radio in a friend’s 1949 Buick. This car actually has 6 volt electrics but the RediRad will work equally well on the 12 volt supply found in P4s.

Delivery was very quick and the unit arrived complete with two sets of instructions – the US manufacturer’s manual and the UK distributor’s guide sheet.

The RediRad is housed in a plastic enclosure of neat and professional appearance. Installation is straightforward. You simply plug the unit in series with the car aerial lead (the required connectors being already fitted), then connect the black lead to the car frame and the red lead to a switched battery feed. Any such feed should be fused. More guidance on this is given on the UK distributor’s guide sheet and it’s important to read this thoroughly. In my case, I connected the red lead to the radio’s own on/off switch, so the RediRad would switch on and off with the radio. if you do this, it might involve opening up the radio.

With positive earth installations, particular care is needed to ensure the RediRad’s audio input connector never touches the car bodywork when it’s lying around unplugged. A safety shroud is included with the kit for such cases. This precaution wasn’t needed in the Buick, or other negative-earth installations.

Once connected up, the RediRad can be secured anywhere within range of the leads with the two cable ties provided. I attached mine to the bottom of the radio.

You now switch on the radio, and it works exactly as normal. When you want to listen to your own music, you connect your audio source to the unit’s 3.5mm jack and tune the radio to 300 metres on the medium wave band. In my case I set one of the Buick radio’s pushbuttons to this wavelength for easy selection in future.

For my audio source, I plugged in my Samsung S5 phone and tried playing some music. The sound quality out of the radio was excellent. However for good results I found the phone’s volume needed to be set to about half; it was possible to overload the RediRad by turning the phone’s volume up to full, causing distortion. The radio’s own volume and tone controls worked as normal of course, just like with any other radio station.

When the RediRad is in operation it cuts out reception from ‘normal’ broadcast stations which might compete with its own signal. This is a wise precaution since otherwise there could be background whistles.

When your own feed of music (or whatever) stops, or you unplug your audio source from the RediRad, reception of normal stations doesn’t return for a while… in mine this took 45 seconds. This puzzled me for a while and I thought the RediRad must be faulty, but it wasn’t! If you think about it, unless that delay was built in, the Redirad would immediately switch back to normal radio reception whenever there were silent gaps on your own tracks.

All in all, I can recommend the RediRad. It is easy to install and provides a very good sound – if anything, better than normal radio stations. You can plug it into almost anything.. CD players, MP3 players, smartphones (through which, in favourable locations, you can tune into internet radio stations whilst on the move), mini FM or DAB radios… you name it. If you use your P4 radio a lot, I think the RediRad almost comes into the category of an ‘essential’.

I have no connection with the RediRad besides being a satisfied customer.


The appearance and sound quality of the radio in my 1966 car good despite being a LW / MW Mono output unit. Unfortunately, there are nowadays nearly no radio stations worth listening to still broadcasting on MW/LW. I did not want to go down the route of converting to negative earth and fitting a modern stereo, and wanted to retain the original unit and sound quality.

The low cost easy solution is a ‘wired modulator’. There are a few variants available in the marketplace, but the one I have settled on is the RediRad™, designed and manufactured in the US. What this does is connect to an iphone, mp3 player, smartphone, CD player, or whatever device you have that outputs sound via a 3.5mm output socket, directly to the original radio via the antenna lead. The unit is small (a little larger than a pack of playing cards) light, and easy to connect. The case seems sturdy, and the wires, particularly the antenna male & female leads are of a very good quality. The US manufacturer tells me thousands are in use in the US, and around 100 a year are presently sold to UK customers who order direct at a total cost of around £130.00 once shipping, import charges and UK VAT has been added. An online search reveals all favourable reviews spanning the last 7 years or so since launch.

Instructions provided are clear, although in ‘American’, and adapters to allow connection to existing fused power supply are included. The power and earth wires are around 5 feet long, the 3.5mm jack lead is around 6 feet long. The antenna connectors are shorter because it is designed to be located near where the antenna lead enters the radio itself.

The unit is designed for the very widely used ‘Motorola’ type aerial lead connectors, but adaptors are widely available for around £5-£10 online if your car or radio is fitted with a different set up.

There is an online video showing the installation process in a 1980’s BMW. Again, the speech is American but most should be able to cope. Search for ‘RediRad™ BMW Installation’ on a well-known video hosting site.

The only difficulty if there is one, and this will vary from car to car, is the routing of wires etc.

  • Unplug radio antenna from radio.
  • Plug RediRad™ into Radio antenna socket.
  • Plug Antenna lead into RediRad™.
  • Electrical connection is one to an ignition controlled power supply, and one to earth.

That’s it, and you are left with a lead (with a 3.5mm jack) to plug into whatever you would like to play. I have placed the unit in my car behind the facia just on top of the radio itself, secured with cable ties (again included in the pack). The only visible sign is when I draw the auxiliary-in lead from it’s hiding in place in the dash cubby hole. Connect up the player, and tune in on the radio to 1000KHz (the ‘10’ position on some radios, or 300 metres MW.) I have tried an mp3 player, Nokia smartphone and an iphone, and all work fine. (The negative earth FM version tunes to 91.1).

Available for positive & negative earth cars, 6v or 12v, AM (LW/MW) or FM. The sound quality is as good as your radio amp & speaker can muster, and I like the tone of modern music on my cars single 6” speaker. Not just for music; plug in your smartphone and you have effectively got a hands free installation, (and in my car the unused ashtray is the perfect cradle for a phone) with the inbound call being heard through the radio speaker(s), as you would with a modern hands free system, and if you want to use the satnav on a phone, again, it will play through the radio. Tip; Don’t have the volume on your input device on maximum, between half and three quarters is best, it will vary from device to device, and then control radio volume as normal.

Please carefully read the information below, I will answer any questions I can, or get an answer from the manufacturer for you, or see for yourself at and download a pdf version of a manual.


Please note this is not my day job, but an extension of my interest, ownership and enjoyment of classic cars. If you see the order details below, there is sufficient information to easily identify I have a very full time occupation already.

Order by sending an email to me or use the contact details below.

I require an email order as you will be sent an emailed ‘paypal’ invoice (you do not need to have a ‘paypal’ account to pay) and to avoid errors or misunderstandings I request a detailed written emailed order as follows:

  • Name of Car Club?
  • Make & Model of Car?
  • Make & Model of Radio?
  • 6 or 12 volt?
  • AM (LW/MW) or FM version required?
  • Positive or Negative Earth? (This last point only applies to AM (LW/MW) versions.)

Optional Extras: Please tell me in your email if you require any of these items:

‘Royal Mail Next Day Insured’. (+£5.00)

3 terminal single pole double throw switch_500x500

‘Period’ 3 terminal single pole double throw switch. (+£5.00) See notes below about 2 or 3 position ignition switches to see if you might want one of these.

Piggy Back Spade Connectors_500x500

‘Piggy Back’ 1/4″ (6.35mm) Receptacle Spade Connectors £0.50 Each.

Orders will be posted next working day after receipt of cleared funds. If sold out pending fresh stock from the US, I will not invoice you until stock replenished and will let you know when to expect your invoice.

I can take phone enquiries, but I am often away from my office so email would be more efficient, and I don’t want to rack up huge phone bills returning calls for what is just an extension to my hobby.

I am very pleased with the RediRad™, and I didn’t know the old radio in my car could sound as good as it now does. As to transferring from car – car, well if I had more than one car that I used regularly that did not have FM or CD player I would probably install a unit in each, and would consider it an added feature when it came to sell the car.

I am so impressed I have arranged direct with the manufacturer, to offer units to members of the classic car clubs at a discounted fully inclusive cost, and they will be sent by ‘Royal Mail Signed For’ from my UK address, so no hanging around for Customs clearance etc. like I had to.


Online from various US sources they can be bought for around $100.00, but shipping and import charges (including VAT) mean the total price paid by UK buyers is around £130.00, plus the delays waiting on Customs etc. I have seen cheaper variants from China (although western ‘branded’) but these don’t have the track record of the RediRad™.

I am so impressed I have arranged direct with the manufacturer, to offer units to members of UK classic or collectors car clubs at a discounted fully inclusive cost, and they will be sent by ‘Royal Mail Signed For’ from my UK address, so no hanging around for Customs clearance etc. like I had to. Total inclusive cost is £110.00 and this includes the one RediRad™ as you specify, (see below) installation instructions, alternative fuse connectors, cable ties, import duties, shipping and delivery to a UK postal address by ‘Royal Mail Signed For’ service.


Electrical Draw

  • The FM model ‘idles’ at around 7 milliamps (0.007 A) and draws about 40 milliamps (0.040) in RediRad™ mode.
  • AM (LW/MW) models ‘idle’ at around 25 milliamps (0.025 A) and draw about 150 milliamps (0.150 A) from a 12V system in RediRad™ mode.

Two position or three position ignition switch.

On most cars since the 1970’s, the ignition switch where fitted has three positions. 1.Off, 2. Accessory or Battery, 3. Ignition, with a sprung fourth position or starter button to start the engine. The RediRad™ is connected to the Accessory or Battery position, or another source energised by this position on the switch. However, many older cars, including my, have only a two position switch; 1. Off, 2. Ignition and then a sprung third position to start, or a starter button. In these cases the RediRad™ is connected to a switched supply. On my car, I chose to ‘piggy back’ the supply to the fan heater switch but it could be any ‘clean’ fused supply. By clean, I mean not on the ignition, fuel pump circuit or indicators circuits.

Types of Ignition Switch: IMPORTANT.

Owners of cars with three-position ignition can therefore use their radio and RediRad™ whilst parked, with the key in the Accessory or Battery position, as they might with the existing radio. Owners of cars with two-position ignition cannot, as to have the ignition on without the engine running means the fuel pump (if electric) will be running, and the coil and ignition circuit will get hot with high risk of failure. I modified the installation so that I could use the system whilst parked. (The radio was always directly wired on such cars). I have fitted a discrete 3 terminal single pole double throw switch. (Mine is concealed in glove box.) This is wired as follows:

  • Terminal 1. Power in – Ignition controlled from ignition switch or fuse controlled circuit. In my case the heater fan switch.
  • Terminal 2. Output to RediRad™
  • Terminal 3. Power in – permanent supply (piggybacked off cigar lighter in my case.

Default position will be power from terminal 1, but if required, I can throw the switch and use whilst parked without risk of damaging ignition circuit components or fuel pump running.

Positive Earth Applications Only: Three Very Important Notes.

1. Input Device Chargers.

Almost universally, modern devices and in car chargers are for negative earth only. There are workarounds but they are unreliable from what I have read so it is far far safer to just do not charge a negative earth device (e.g. iphone) in a positive earth car. CHARGE AT HOME, USE SAFELY.

2. Metal Cased Input Devices.

For the reason linked to the charging issue, if your input has any external metal casing, ensure it does not earth itself against car metalwork; use a NONCONDUCTIVE case, or place in a NONCONDUCTIVE location e.g. plastic or upholstered.

3. When Not In Use.

Use the protective cap supplied for the aux lead so that when the RediRad™ is energised but not in use, it cannot earth itself to car metalwork.

I hope this covers all the bases, but I will answer any questions I can, or get an answer from the manufacturer for you.

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