Coax Cable FAQ

C-5 Galaxy

Q: What kind of cable do I need for my outdoor antenna?
A: Basically speaking, you need a 50 Ohm coaxial type cable, or what's commonly referred to as 'coax'. This type of cable comes in numerous sizes and brands. The larger (thicker) the cable is, the less signal loss you will have on long lengths.

Q: How does cable signal loss affect performance?
A: The longer a cable is, the more signal loss you have as it flows through the cable. This effect becomes more pronounced as the frequency you're using goes higher. For instance... If you had 50' of cable, there would be more loss while operating at 900 MHz than there would be at say, 40 MHz. Typically losses for a cable are listed at different frequencies, based on a 100' length. As an example... A 100' piece of LMR400 has a loss of 1.5 dB at 150 MHz and a loss of 4.0 dB at 1000 MHz. As far as real world performance is concerned, you really aren't going to start noticing a difference until it's at least 2 dB and higher.

Q: Will I have loss using a small cable for a short length on a longer big cable?
A: No... This is a common misconception. Signals don't move through cable the same way water moves through a tube... You don't get a blockage at one point by using a smaller cable. Say for instance you have 100' of LMR400 cable, and then you use 3' of RG58 for a flexible patch cable at the end... Only 3' of the small cable isn't going to change anything, because even at 1000 MHz, that would only come out to about .49 dB of loss. Yes, that's something, but you would never actually hear it. Now if you ran the whole length with RG58, then that would be bad.

Q: What are the basic cable sizes?
A: In the US, the two designations you see the most for cable sizes are 'RG' and 'LMR'. The 'RG' designation is used across numerous brands, whereas the 'LMR' designation relates to the Times Microwave brand of cables. The actual physical dimensions for RG and LMR sizes can often be the same, but sometimes there are slight differences. The way they try and make this easier to understand is that the industry assigns a "Cable Group" letter to both cables and connectors. For instance... Times Microwave LMR400 and Belden 9913 are both considered "Group I"... They're both technically an RG8 size cable that physically have the same overall outer diameter and center conductor diameter. So in this case, the same connector would work on both.

Q: So what exact cable choices do I have?
A: See the chart below... These are some of the most common cable choices available for typical communications applications. All are 50 Ohm and tend to be listed from lowest loss (top) to highest loss (bottom), but not in exact order. Check manufacturer specs for the exact loss numbers for each band, on each cable.

Q: That's all great, but what do you recommend for the average setup?
A: We like to recommend Davis RF 9914F "Bury-Flex" as an all-around good cable for any run longer than 40'. It's a very durable cable and can be put underground as well. It has a loss rate very similar to LMR400, but its multi strand center conductor makes it much easier to work with... The cable is flexible enough to attach directly to many smaller radios without using a smaller patch cable, and can be used directly on rotators. Flexibility is good to have, because it allows you to do things without using patch cables, which means less connectors/adapters and less things to break. It can also be used directly on SBS-1/ RadarBoxes as long as you provide some physical support for both the cable and box (though it looks kind of silly). If you're going 40' or shorter, you can usually get away with RG8X size cable, though that could still give a noticeable loss with higher bands like 800-1000 MHz. But for VHF it would be fine.

Q: What about cables like RG6 and RG59?
A: RG6 and RG59 are 75 Ohm cables that are primarily designed for TV work. Yes, many people have used RG6 for receive purposes and it can work OK, but it's not the proper cable to use in communication applications... You'll probably have to use adapters to do so, which is never a good idea. Most comm equipment is designed to be used in 50 Ohm systems. Some manufacturers offer RG6 cable with their antennas, simply because it's more plentiful and cheaper.

Q: What's with all the different connector types?
A: Yes, there's many different types of connectors. Forget about 'F' connectors, because those are for RG6 and that cable shouldn't be used for communications. Same goes for RG59 & 60 connectors. Many of these come in a 'crimp' style and 'clamp' style, and are available for most popular cable sizes. Crimp style is less water resistant on exterior connections, but it can be physically stronger on the cable. Clamp style has a small rubber gasket which helps keep water out of the cable, but it can be a physically weaker connection to the cable. Some of these connectors can be available in both 50 Ohm and 75 Ohm. 50 is what's needed in communication applications.

Q: So what connectors do I need to use on DPD Productions antennas?
A: All of our outdoor antennas use 'N' Female connectors. So you would need a Male 'N' on the antenna end of your cable for those. If you already have cable with UHF connectors on it, we don't recommend them, but we can put a Female UHF connector on the antenna for you. Our interior Blade model antennas and mobile antennas often come with a Male BNC connector, but we can also put other types on if you need it. Sometimes we can also figure out ways to hook things up to more odd equipment, like older Motorola "Universal" connections and other things.

Q: How does it work if I want to use a rotator?
A: You either have to use one main cable that is flexible enough to be rotator safe, or use a separate cable up at the rotator that is more flexible. The easiest way to do it, is use a multi strand flexible cable like Davis RF's "Bury-Flex". Then you just leave enough slack up near the top by the rotator so that when it spins all the way around 360 degrees, it will be lose enough to bend.

Q: I can't make cables, so who could do it for me?
A: We do offer RG8X cables, but if you need larger sizes... Davis RF is a good company to contact. They can use the cable you prefer and put the connectors you want on it for a fee.

Q: What cable can I use on my ADS-B Box?
A: The SBS-1 uses a BNC connector. The SBS-1e and RadarBox use an SMA connector. Some of the new little USB receivers use an MCX connector. You will need to use an adapter for MCX, because MCX was never intended to be used with standard 50 Ohm cables. Because the ADS-B system operates up at 1090 MHz, loss can be a real issue with cable. Using a low quality cable could really degrade the signal coming into your receiver. We recommend a full RG8 size cable for anything longer than 30'. If you want to use a single center conductor cable, it's going to be very stiff and difficult to work with. If you choose a flexi style cable with a multi strand center conductor, it will make it easier. SMA connectors are very small, but people have reported successfully using an SMA on an RG8 size cable, and directly connecting it to the box. But it's very important to reinforce both the cable and box by using velcro or something, to hold them both down on the table. We also offer flexible patch cables as an option, with our ADS-B outdoor antenna.

Size Model Maker Group Center Notes
1/2" LDF4-50A Andrew
L1 Single This cable is moving into commercial grade. It's very stiff and difficult to work with.
5/8" LMR600 Times Microwave L2 Single Very stiff. This cable would need a smaller patch with anything less than the biggest desktop radio.
5/8" LMR600UF Times Microwave L2 Multi Strand More flexible than the single conductor version above, but still big and difficult to work with.
1/2" LMR500 Times Microwave L1 Single Very stiff cable and will most likely need a smaller patch to work with anything but the largest radios.
RG8 9913 Belden i Single 9913 has been around a long time, but sometimes water seepage can be more of a problem on this cable.
RG8 9913F7 Belden i Multi Strand This is the more flexible version of regular 9913. This can be easier to work with.
RG8 9914F Davis RF i Multi Strand Known as "Bury-Flex". This cable is a very good all around cable and fairly easy to work with. It's flexible enough to be used with rotators and can often go directly to radios without a smaller patch.
RG8 LMR400 Times Microwave i Single 400 is an all around good cable. It doesn't seem to exhibit water problems as much as 9913, but it's still pretty stiff and can be difficult to connect directly to smaller radios without a patch cable.
RG8 LMR400UF Times Microwave i Multi Strand 'UF' stands for "UltraFlex". This cable is more flexible and easier to work with than the regular 400.
RG8 Flexi-4XL Wireman i Multi Strand This is another multi strand flexible RG8 cable that offers.
RG8 Super 8 Wireman i Multi Strand Slightly more loss than the Flexi-4XL, but also flexible to work with.
RG213 Various Various e Multi Strand More popular in Europe than the US. Typically has a 7 strand center conductor. Somewhere between RG8 and RG8X in terms of loss. Harder to find connectors in the US. Better to just go with RG8.
RG8X LMR240 Times Microwave x Single Same outer dimension as regular RG8X, but slightly less loss due to solid center conductor. Too stiff to use in most mobile applications.
RG8X LMR240UF Times Microwave x Multi Strand 'UF' stands for "UltraFlex". Basically the same as regular RG8X. More flexible than regular LMR240.
RG8X "Mini 8" Various x Multi Strand RG8X size cable is offered under numerous brands. The 'RG8' designation is misleading, because it's considerably smaller than RG8 size cable. RG8X is good for runs shorter than 25', patch cables, and mobile applications.
RG58 LMR200 Times Microwave c2 Single Same outer dimension as normal RG58 cables, but center conductor is slightly larger, so it often won't fit in normal RG58 connector pins.
RG58 Various Various c Both RG58 comes in both single conductor and multi strand variety, and many different versions. Bottom line, this should only be used in mobile applications or in very short runs.