Recording and Playback

Introduction:

 There is a saying that more audio/ham gear has been bought and sold because of on-air recordings than most any other reason. This is especially true amongst audiophiles. You may have heard many of us seemingly mindlessly and endlessly recording and re-recording ourselves on the air. You listen and maybe think these guys are nuts or I don’t hear any differences. Hopefully you do hear some difference and maybe you have wondered how it is done and how you could get into doing it, even if you have no interest in working in Enhanced Audio (EA).

 It is fun and sometimes quite eye opening to hear ones self on the air and hear what others are hearing from your station. Sometimes it is a welcome surprise, but sometimes you may get a little upset as you did not realize that you did not sound as good as you thought you sounded. First let me interject that there are a lot of factors going into what you hear coming back off of an on air recording. Never and I mean never make major adjustments or sell or buy new equipment based on just one recording. There are so many factors that could miss-lead you that I would suggest that at a minimum you listen to 3 recordings on 3 different QSO by at least 2 hams before making any change.

 The skills of the recording ham, band conditions, equipment used, and signal strength are just a few of the factors that could influence a recording. Each recording ham and each recording session change these variables.

 When doing recordings you must ask for the permission from the ham being recorded before doing so. Never just record and then play it back. Who knows he may not want it done and you have now violated a FCC regulation. Just make it a practice to ask if they would like a recording and then say “playing it back by the request of the ham”. Of course if you have been experimenting on the air with another ham good sense would indicate that there is an implied consent each time if it was given in the beginning of the QSO so announcements don’t have to be done needlessly.  

 Getting the audio out of the rig into a recording device:

 I suppose you could put a recording device next to the rig’s speaker and record off the air that way and when you play back you could hold the microphone next to the speaker of the recording device and play it on the air. This could be done, but I guarantee you that the quality, fidelity and faithfulness of a recording done this way would be very much lacking.

 There are a lot of devices manufactured these days that you could select to be used for your recordings. Some rigs have a built in recorder, but most as I have had experience with are really meant for short recordings of things off the air or pre-scripted messages for things like contesters. Not really for on-air recording and play back. You can use a sound card on your computer. You could use a mini-disk recorder. You could even use a cassette recorder or real to real recorder. There are even solid state memory devices these days that could be used. So what medium you chose is really up to you and you can make that decision based upon your own needs and wants.

 Ok we have decided that the off the speaker method is not going to be used. How are we going to get that audio from the rig to the recording device. I know when I first started that was my biggest question. Well of course we are going to use a piece of wire. The wire used should be of good quality. It should be shielded to lessen the chance of our old friend RFI getting into the recording by mistake. You can get good quality wire form many commercial places. I have even used the stuff at Radio Shack, but make sure it is shielded. Much of their stuff isn’t so ask before you get it.

 Ok I got some cable or I am going to get it, but first where to I connect the cable on the rig and the device? There are a couple of answers to that question. There is a way that will work and the best way. Most rigs have a place to connect an external speaker. You could take the signal off there by either disconnecting the speaker or using a splitter to take the audio to the recording device and the external speaker. The problem in doing it this way is of course you will control the strength of the signal to the recording device by turning up or down the gain on the receiver. If you are going to a sound card, or other device you have the possibility of overloading the input in this method. You could make a connection via the headphone jack. This is about the same as the speaker connection as it is influenced by the gain of the receiver and in this method you will have to use a splitter method so that you can still use your headphones. The best way is to take the “Fixed Audio” out of the back of the radio. Most newer rigs have a place to do this. Some of the Yaesu rigs have an actual fixed output jack. Others that I have worked with like the Kenwoods and Icoms, have the fixed audio available in a din plug on the back. Of course the advantage of this method is that the level of the audio is not affected by the gain of the receiver. The type of plug on this end of the cable depends on the connection on the back of the rig. So check this out before you buy the cable because you may be able to get a shielded cable with at least one of the correct connections already pre-made. So now we can get output from the rig so we need to plug it into the device we are going to record on. If it is going to be a computer sound card, the usually have mic and or line input to the card. Use the line input if there is one. If there is none you can go into the mic input but remember you are probably way too hot for that port. Line to mic input does not match. You will have to step the signal down from line level to mic level by building a matrix and a line transformer to keep hum off. Again the best way is to go into the line input of the card and the most cost effective and fastest way to do this if there is no line input may be just to buy a new sound card that has line input. It is up to you. There are lot of places where you can get a description on building the matrix even on this page. Hint MURF BOX. Now once we have the audio going to the computer we have to think of our return path to get it back into the rig. Other devices like min-disks usually use RCA jacks and in this case if you have a Yaesu for instance you could just use a good quality shielded RCA patch cord. For other radio manufactures you would have to solder into the din plug on one end of the cable and put an RCA on the other. Most of these type of devices expect line level input and have level input adjustments built into the device with indications of overdriving.

 Getting the audio back into the rig:

 Getting the audio back from the recording device could be just a cable with the proper plug on one end of the device as it connected to the recorder output to the mic input of the rig. Remember here again we have a miss match line level to mic level and you will have to deal with it. Also two signals coming into the mic even if they are not at the same time just opens the door to problems like RFI, hum and distortion on you normal and recorded audio. You would need to wire or splice the signal into the mic connection. I really do not approve this method as most everyone I know does not recommend it either. But, it can be done.

 Now is the time I need to introduce you to another piece of equipment that will make recording and just about anything you do with audio a lot easier. Even if all you are going to ever do is plug your stock microphone into the rig, you should consider replacing the mic plug with an XLR plug and use a MIXER. A Mixer will allow the routing of many audio related devices back and forth between other similar or dissimilar devices. If all microphones you have, be they stock microphones of Heils or any other type, have them always come with or convert them to XLR and put them to a mixer and build one path to your rig be it to the mic input or the back of the rig. You then can easily switch microphones for testing or for just having fun without worrying.

 Mixers in Ham Radio Use:

 Mixers can be bought at most music stores or guitar shops or audio stores. They are readily available at commercial audio stores on the internet. Check this page out under commercial links to find some good sources. They can be gotten for as little at $50.00 to many thousands of dollars. For most ham related activities I would think spending more than $200.00 for a mixer would be over kill and the ones for less than $100 are in most cases even more than you will ever need in ham radio.

 Basically a mixer lets you plug input devices either XLR or TRS (look up these terms on the internet for a description), mix those inputs with other devices if needed and route the output out the main mix channel to another device in line. There may be other output auxiliary channels that can be used as well. I will not go into that much about how mixers work here but the information can be downloaded from manufactures like for instance Behringer. Most mixer have at least one other feature that is handy and that is a small EQ built in. There is also a headphone jack that can be used to monitor what is going on in the mixer.

 Ok, we got our little $50.00 mixer now what? Lets say we have our microphone XLR input to channel one on the mixer. It is a dynamic microphone so no phantom power is needed. Phantom power 48 volts is usually supplied on mixers along with mic preamps. If you want to use a condenser microphone you will need phantom power. Anyway back to recording. I would take the fixed output from the back of my rig and rout it to another input channel on the mixer. Probably via a din plug to TRS cable. Now by pressing a button and sliding a slider on the mixer, I can route the output of the rig to an auxiliary channel on the mixer to the line input of the recording device. In my case it is a mini-disk recorder. I know this sounds complicated but it really isn’t. If you got a little mixer and played with it and tried to route audio back and forth, you would see that it is not that hard.

Now of course we have to get the audio out of the recording device back into the transmitter. This is made much easier now in the all we have to do is run a shielded cable from the output of the recording device to the mixer in another channel. Now you can see why having enough channels on a mixer is important. In this case the audio signal coming back form the recording device is allowed to just go out the main mix to the transmitter as though it was coming from the microphone. Remember that the regular mic audio goes into the mixer in a channel and comes out the main mix. Mixers also allow you to build an external rack system with EQs and other devices and have them mixed onto the main mix and not just use the plain old mic by itself. But that is up to the amateur if they want to get into doing audio enhancement. In either case the recording and playback path is built and can be expanded upon if needed.

 EQing Ham Radio Recordings:

Ideally, you would want the recordings you are doing to be as accrete and truthful as possible. But for a lot of reasons that is harder to do than it sounds. The recording devices themselves are pretty good. Computer sound cards have come a long way and other devices designed to just that job are very capable of doing a great recording. The problem is that we are doing it live over the air, which interjects other problems. QSB, QRN, and QRM in ham talk are some of these conditions. When a marginal signal is transmitted over long paths, it has a tendency to lose some of the high frequency tones. The result can be muddy or overly bassy audio. The highs are the first to go. You may want to turn your RF gain down on your rig to eliminate some of the static. The resultant recording will sound better but you may have truncated some actual audio along with the static noise so important audio information the listener was trying to hear, like the sound of RFI or other imperfections would not be heard.

 The last thing you would want to do was to EQ the recoded signal to such an extreme that the recorded ham would get the idea that his audio was better or worse than it was because of your EQing skills. But because all receivers are not absolutely flat you may see that your receiver is actually stamping itself on all recordings. A way to correct for this is to use a graphing program like HamAlizer or SpectraPlus and graph some white noise and see if the line is going fairly straight on the graph in relation to the bandpass of your receiver. If for instance you can see that there is a sharp roll off anywhere, you can EQ those frequencies to bring it back to as flat as possible. For most hams this is over kill as they are just looking for a ball part of how they sound. But for some of us freaks, we endeavor to be as accurate as we can be so we take this extra step. In most cases if you are using a Mixer the small EQ on it can be used, but if you have another EQ or even a side of another EQing device it can be used to do the recording flattening.

 Recording Transceiver Rules:

 One of the things you have to remember other than having all switches and knobs set correctly during a recording, is that you can not record a signal that is wider than the bandpass of the receiver you are listening on. For instance if I am recording a friend of mine and he is on his SDR1000 Flex Radio and is transmitting to me at about 4Khz, I will not be able to hear or retransmit his signal on my ProIII with it’s greatest bandpass off 3.6Khz on receive and about 2.9Khz on transmit. When he heard the result of the recording he could easily hear the loss of over 1Khz of frequency and depending on how I listened to him I would have bass or highs missing and it would sound very bad. If I wanted to do a faithful recording of his SDR I would have to use my Kenwood 850 with the DSP-100 set at 6Khz and then I could capture and playback everything. I know we are talking about some extreme wide signals here, but I do it to illustrate the problem. In most regular ham applications we are talking about being able to record 2.7Khz or so and if you pay attention many rigs can hear and playback audio at least that wide. The problems is that the guy doing the recording may forget and have his radio set as he has it for a contest or something like 1.8Khz and can’t figure out why it sounds so bad. So pay attention that you have your rig as wide as you can when doing recordings.

 Recording can be fun with ham radio. It is not just for the HI-FI ESSB or EA audiophile. You can use it to have prerecorded messages for calling CQ or Contest messages, or just to record yourself and others while you are busting that major pileup. So don’t limit yourself if you are not into all this audio stuff. There are a lot of uses for recording in amateur radio, but please do a good job. I get people trying to give me a hard time sometimes around 14.178 and always know it is not an audio ham as they do such a poor job. Have fun with it but don’t QRM others.