A Vintage Antenna and a modern Auto Radio??
Earlier this year I finished restoring and installing couple of original 1950 GM Chevy radios for my self and a buddy. I used a reproduction of the original antenna thatís sold by the repro vendors. Both the radios work and sound just great, they are clear and plenty of volume, but they are only AM radios.
So, to give me the ability to play a CD or grab an FM station I installed an under dash Sony CDX-GT420U stereo from Crutchfield that slips in and out with just a push and a plug. Since Iím not looking for that super hi-fi sound that the younger generation seems to need, I just slipped a couple of inexpensive oval speakers in each of the doors.
The CDís sound fine, however in the radio mode itís very, very bad sounding whether it in AM or FM. Itís not clear, the volume is weak, the signal drops in and out in both the AM and FM. It sounds like itís not connected to a good antenna. Iím using the same cowl mounted antenna that I use for the original Chevy tube radio with a Y splitter/adaptor.
The Sony runs off of a voltage booster and I measure 12v supplied to the unit.
I was in a Best Buy store the other day and asked the clerk if they ever had this kind of a complaint about these aftermarket radios and he said yes, a lot of them have poor radio reception and the installers put antenna boosters in them. That just sounded like BS to me, I would think that todayís radio technology should out perform a 60year old radio hands down.
Anyone care to comment on this???
You got to face it, how many of these aftermarket sets are sold only for their AM reception?
A lot of these sets work quite well on FM, but they are definately lacking in the AM department. Most people don't listen to AM on their car radios anyway, so any engineering effort put into making a good AM receiver would not pay for itself.
(Connoisseur of the cold 807) CW forever!
Yeah but Curt, the FM is just as bad as the AM side of this thing, and my $1 garage sale Magnavox pocket radio almost sounds better than this $150 Sony Stereo. I can't believe that these are that bad at radio reception. When the kids in the electronics section have them cranked up so you can hear them all over the store they sound just fine and dandy. There has to be some sort of a twist involved here with using the original style antenna or something.
I would recommend disconnecting the Y adaptor and connecting the antenna directly to the Sony radio. The antenna coil in the Chevy radio could be loading down the RF circuit in the new radio. I agree with Curt, with the new radios, the AM section is an afterthought. When restored properly, the old tube auto radios will outperform the newer radios, handsdown. Harry
I could not have said it better Sony system and found out it was crap. I suggested He take it back and trade it for an Alpine Radio.The best advice I could give Him. He was as pleased as Punch with the Signals and no Fading on FM, and superb sensitivity on AM. And a Price that was about the same., have something to glow about!
Ham and GROL Licensed
First off, you need to determine whether the problem is bad power to the radio, a bad antenna connection to the radio, or a bad/cheap radio.
If your car is 6 volts, you need a voltage booster. There is also such a thing as an inverter for positive ground, as someone else mentioned, but Chevy's are negative ground. Where did you get the voltage booster that you're using? It may not be adequate for your stereo. Custom Autosound makes one; Antique Automobile Radio makes a heftier one. You will never get 200 watts out of one, but you should indeed get enough power to turn the music up loud and not have distortion. When in doubt, remove the stereo and connect it to a 12 volt battery or power supply.
Antenna: a bad antenna or lead-in can certainly affect reception, but even with reduced sensitivity the stronger stations should sound clear. Still, it's easy enough to check. Connect the antenna directly to the radio, or use another antenna -- hold it out the window long enough to see if reception improves.
One more thing to keep in mind, going back to power: as you know I specialize in converting radios and selling stereos to fit antique cars. The single biggest complaint I get from customers is that the sound is distorted. It sounds just fine when the volume is low, but turn it up and it sounds awful -- particularly the bass. It sounds as though the speakers aren't very good, even though they believe they purchased good quality speakers. The problem? Resistance in the wiring, either 12 volts to the radio, or grounding the radio to the frame of the car. If you have say, 1/2 ohm, at low volume you'll have 13.5 volts instead of 13.8 -- certainly not enough drop to hurt anything. But -- turn that volume up, and those bass notes will make the radio draw up to 10 amperes instantaneously. That voltage drop is now 2-3 volts, and definitely enough to starve the amp. The result is a distorted bass, sounding as if the speaker can't handle it.
Now -- you said that CD's sound fine but the radio is bad. I would tend to think the problem is a bad radio; but check these other things and see what you find.
See if there's any mention of an antenna trimmer on your new radio. The old ones used to have an adjustable trimmer to peak. You found a weak station around 1400 on the AM dial and peaked the trimmer for the most volume. There used to be a specific length you set the antenna to for best FM reception but it's been too many years since I've worked with this stuff to remember.
Radiodoc, no trimmer on the new radios.
Gary, I was hoping that you would check in, I knew if there was an answer about an auto radio question you would be the man. As I mentioned earlier, this is a stock 1950 Chevy truck. The original radio was restored last spring by me and I installed a brand new reproduction, period correct cowl mounted antenna. The hole was drilled new and all the grounds are clean to bare metal, no rust on this truck, the underside of this dash is ďcleanĒ bare metal and all of the battery and engine grounds and cables are new with the connections cleaned to shinny bare metal at the frame. It does not see the weather and is kept inside all the time. That original radio instalation works just great, absolutely no problems, not even ignition noise as I have all of the electrical suppression installed that is called out in the original Chevrolet installation sheets from that era. I have another new telescoping antenna mounted to a metal sheet that I use down on the test bench and I've temporarily swapped this antenna for the one mounted on the truck and grounded the mount to the frame with the same results. The antenna leads and the 'Y' are new and show no measureable resistance. I would think that should eliminate a bad antenna system.
The Stereo unit is the typical mid range unit that you would see on any ďwall of radiosĒ in any of the big box stores. The lack of performance that I am talking about is not a tiny little barley noticeable bit of poor performance, no nit picking going on here, and again, Iím just expecting from it, a low level of performance at relatively low volume levels the same as I would expect from the original tube radio. I am 66years old not a not an audiofile nor a teenybopper looking to wake up the neighborhood with 400watts of stereo output.
The power booster I am using is the one sold by Custom Autosound out of Anaheim, Ca. (NGVB-HC) and as you know it is sold universally by all of the vintage vendors. It is made specifically to power negative grounded radios and accessories. It is rated at approximately 3-5 to 4 amps output which should be well with in the range that this radio will be operating in driving two small door mounted speakers. Iím outputting 12v and also use the booster to drive a small electronic tach that I have temporarily installed. The radio performance seems to be the last thing to go when the battery gets drained down to point where it wonít start the car. At least thatís the way I remember it from 50years ago while parked out behind the cornfield with my girl friend.
The speaker wire is the typical 14ga clear/blue wire that is sold at Radio Shack or the automotive stores and the leads are less than 6í long each. Just like the speakers and stereo unit itself they transmit Ricky Nelsonís sounds from the CDís just fine.
And not to pi$$ anybody off but the idea that one should expect poor performance from a brand new piece of electronics equipment just doesnít seem logical to me. If I go down to a consumer electronics store and buy a good, name brand, midrange, entertainment unit, to say that when I get it home and plug it in I should ďexpectĒ poor performance from it, make now sense to me at all. Even the poorest performing unit out there would have good reception from WGN, a 50,000watt AM station that is only 30 or so miles away. I canít believe that the consumer would put up with that for any length of time before the manufacturers like Sony, etc., would be swamped with returns.
I have not removed the unit and taken it down to the radio bench in the basement to test it. I'm just assuming that the problem lies in or around the truck somewhere. I'll see about pulling it all out of the truck this weekend and setting it up on the bench with a 12v battery.
Interesting little tidbit about those voltage boosters: Antique Automobile Radio designed the original one and not long after, Custom Autosound began making an exact copy of it. Needless to say this created a little feud between the two. Some time later, the AAR stereo PCB's were redesigned and went from 44 watts to 180 RMS. Suddenly those power boosters were quite inadequate, so AAR redesigned it and built a stronger one. Personally I recommend the AAR version for any stereo; if you're using a small device such as a tach or clock, the CAS version is adequate and costs less -- $59.95 vs. $99.95 for the AAR design.
That being said, I don't believe inadequate current is the problem. If anything the CD player would draw more current, as it has the motor and head mechanism in addition to the amp, vs. the radio with the amp and miniscule draw from the tuner. Plus a power limitation would give you distortion mostly in the bass with the volume turned up -- not reception problems or noise at any volume level. That is UNLESS the booster is in very close proximity to the tuner or antenna wire. The older design boosters are noisy, and quite often they will interfere with AM reception. Even with the new ones, when I install one inside the radio I place a pi filter at the booster input -- two 1000uf electrolytics and a choke. (if it's an inverter, remember the elecs get installed bass -- ackwards)Booster noise only seems to affect AM, not FM.
As for the radios out there, indeed I've heard a lot of complaining about Nissans and Toyotas having terrible reception on AM. It wouldn't surprise me to find lousy reception on a new stereo with AM, but FM should certainly be respectable.
Then again there's one way to find out. Try it out on the bench.
Sounds like the problem Ihad with the radio in my 55 Buick. It did not work well in cooler weather but worked fine on the bench. The problem turned out to be the vibrator.
I read somewhere some years ago that the optimum length for an FM car radio antenna is 31 inches, although using the standard formula, 468 divided by the frequency in MHz, the optimum length seems to be something over four feet, assuming an antenna length optimized for the middle of the band (98 MHz). I also tried it the other way around, dividing the frequency by 468, and came up with just over two feet. I'm not sure now which figure is correct.
Still taint had a chance to get out to the garage. But I did have time to look up the voltage booster at AAR and their part number is exactly the same as that of Custom Autosound that is NGVB-HC, the unit looks exactly the same in both cases and the specs are the same for both, 6-8v input, 13.8v output, 3.7a continuous duty. The only difference I see is that forty bucks.
Now, since you mentioned it, my antenna wire is draped over the bracket about an inch or two from the booster.
Anyway, all is on hold till I get it out and check it out on the bench.
Not being an audio expert or audio aficionado Iím beginning to wonder if the cheapo speakers might be the problem. I wanted to do a relatively inexpensive installation so I used a couple of cheap 4Ēx12Ē 25watt speakers that would fit in through the inspection holes at the bottom of the doors. These were really inexpensive speakers, I mean like both were less than thirty bucks with tax and all. But they were the only ones that would fit in the space that I had. Now the peak output of the unit is listed as 52watts, I donít know whether this is applied to each speaker or split between both speakers or four speakers if you had four.
I live some 35 miles east of downtown Cleveland, maybe 15 miles or so further southwest of the transmitters for most of the AM/FM radio stations in town. My FM radio reception is good on every one of my radios (even the vintage units), except the FM tuner section of my bookshelf stereo. This is an Aiwa CX-NA888 system, bought new in 1999; the tuner section is so bad I need an amplified antenna ahead of it just to get my favorite stations in stereo. I read a review of this particular system a few years back, which stated that the FM tuners in these systems are not meant for far-suburban or fringe area reception, but they will do just fine in near suburbs of major cities or the city itself.
The AM tuner in my system, however, leaves a bit to be desired. While it will receive most AM stations from Cleveland just fine, I hear one station, a local 1kW (0.5kW at night) station just five miles or so down the road from me in the next town, at two spots on the dial--1460 kHz (the station's FCC-assigned carrier frequency) and 560 kHz (0.9 MHz or 900 kHz down the dial). I don't think this is being caused by front-end overload, since the station doesn't run that much power and I am not exactly in the shadow of their towers at five miles away, give or take.
Oh well. I don't listen to AM much if at all anymore since most of the stations (almost every one of them in this area and, in fact, in most cities in the US) switched from music to talk; most of the time I'm listening to one of two oldies FM stations anyway. I agree with others' comments here that AM was included in today's AM/FM car stereos (and home/portable receivers as well, with the possible exception of high performance AM sets such as GE's Superadio series and the older Zenith Transoceanics) as an afterthought. I once owned a Zenith four-mode integrated home stereo system, which I purchased new in 1982, that worked great on FM, but the AM tuner was about as good as a glorified crystal set. The AM section was so bad, in fact, that at night, after sundown, I was hearing shortwave around 1000-1090 kHz! The AM front end of this system must have been very poorly designed. This was in a system that was new over 25 years ago.
I can't help wondering when manufacturers started cutting corners on AM radios. I can understand small, cheap transistor portables having bottom-feeder sensitivity, but in a stereo system? I guess it's as some of you have said here (and as I mentioned above) that AM has been included in these sets as an afterthought; the manufacturers probably feel that people don't listen to AM that much anymore, so they have let the AM performance of their products go waaaaaay downhill; what is worse, they don't seem to care, as long as the AM tuner passes a signal. The focus these days seems to be much more on the FM tuners, as most folks who buy a stereo system today will be listening to FM most of the time anyway.
Just to address a couple of things that you mentioned.
The 468/mc equation is for a half-wave dipole. A 'vertical' antenna like on a car is only a quarter-wave, the car body represents the other half as a ground plane. The typical equation is 246/mc but is affected slightly by the diameter of the vertical element.
Using 246 at midband you see the result is roughly 30".
Image rejection capability runs the gamut on AM receivers. Although your local station may not appear much stronger than others because of AVC /AGC action, you can rest assured that it is if you are hearing images ~910kcs down the band. Its not really overload per se. If the image rejection is rated at 'x' db down then the image resulting from a stronger signal has much more likelihood to be audible. The first stage of RF selectivity determines this rejection capability - images are a normal occurrence with a superhet and the level of the fundamental signal present when tuned 910kc below determines the level of the image.
The shortwave crap that breaks thru as you describe at 1000-1090 kc probably IS overload, either at fundamental freq or mixing with your strong local station.
Proper RF alignment is often the solution but with modern radios as often as not its due to mediocre front end design.
Denny: it can't be the speakers because you said CD's sound fine.
Yeah, that's true Reece, The rest of the replies went right over my head. Living in the far western Chicago suburbs all of my life, I don't ever remember having a problem with any AM reception, of course the FM signal being line of sight and much weaker are alway a problem, dropping in and out and overlaping.
Have you tried another antenna. I had a problem with the antenna lead wire in a Studebaker a few years ago. I found that the original antenna had a broken center wire making reception weak. I just finished rebuilding the radio in my 55 Ford and I put an antenna splitter between the Ford radio and the under dash Pioneer AM-FM radio and the antenna and both radios work fine, the antenna could be your problem. Harry
I think you have a bum unit...
I have two fairly cheap($119 if I remember correctly) JVC AM/FM/CD in different vehicles, CD & FM are great and AM isn't bad... Suspect it could better if I were using a antenna that could be extended...