Stupid electronic purchase

Maine Sail · Aug 2, 2010

Jeff Bacon said:
Hi All:

A couple of years ago I purchased a West Marine (private label) handheld radio that offers AM/FM, VHF, FRS, and Aviation radio channels. I thought it would be fun to listen to planes and to AM from time to time.

The reality is that I get virtually no AM/FM reception, I have never heard a pilot talking to anyone, and the VHF performance is marginal at best. Since this is first and foremost a VHF radio, I am trying to determine how to better the performance.

My initial thought is that the antenna is probably a compromise in order to accomodate all the different frequencies on all the bands mentioned above. If this is the case, how can I determine what type of antenna I have, and am I able to get a different antenna that is purpose built for VHF reception ?

I know virtually nothing about antenna performance, so use small words and type slowly.

Thanks...... Jeff

First, try the high power TX setting, should be a 1 watt and 5 watt setting or High/Low. Second, HH's don't perform that great to begin with because antenna height is an important factor. It may not have anything to do with the fact that it can do AM/FM/FRS and VHF..

Ed Schenck · Aug 2, 2010

So Jeff, from your post it would seem that there is no external antenna. Is there a jack(hole, I am typing slowly) for an antenna? Is there a user's manual with a schematic that shows the antenna? An internal antenna that works at all for line-of-sight(high) frequencies like FM and VHF are useless for AM. But even for VHF and FM you need an external antenna for decent reception.

Don S/V ILLusion · Aug 2, 2010

Jeff
Yes, antennas are designed for specific freq ranges, however, that's likely not the problem.

First, any antenna can be resonant only on a specific frequency. The reality is that any HH antenna must by definition cover a range of frequencies so it is relatively broad band by design. This is true of any marine , ham or any other HH radio so combining them (their functions and freq ranges) into one single unit with a common antenna is neither an uncommon or big problem. There are many examples of this and most work fairly well limited more by the design of the receiver to cover a wide range of frequencies than by any antenna.

If you're still with me, it will always help to use a resonant antenna not because the receiver requires it but the transmitter efficiency and therefore it's range will be greater.

So, not hearing much usually isn't the antenna which as stated is more important for the transmitter end of the HH. Certainly you can buy a separate antenna designed specifically for marine frequencies but the added benefit on receive is minimal so if you can't hear anything now, a marginal improvement won't be very useful.

My thought pattern is definitely crippled by the heat here today so the moral of this story is that your HH is a compromise and like most compromises when trying to serve multiple purposes, they are all equally poor.

CalebD · Aug 2, 2010

Time for the old 'heave ho'.
Jack of all trades but master of none.
Get a HH VHF that works as a VHF. Actually your boat's VHF should broadcast from the top of your mast and get a pretty good range as MS alludes. An AM radio is good for detecting lightning strikes but can easily be a separate battery powered unit. Why do you need to talk to airplane pilots while on your boat anyway? If they are coming to rescue you they will call on VHF ch. 16 as they do a fly by.

kenn · Aug 2, 2010

It's a dud...

Jeff Bacon said:
The reality is that I get virtually no AM/FM reception, I have never heard a pilot talking to anyone, and the VHF performance is marginal at best.

To clarify, if VHF HH antennas are a compromise because they have to cover a broad range of VHF frequencies, wouldn't an antenna that is asked to cover an even broader range of frequencies (AM/FM, FRS, Aviation, VHF ) even be more of a compromise ?

AM and FM in an urban area can usually be received with a paperclip as an antenna, and you've also told us that this HH isn't capable of matching the VHF receiving performance of another HH in the same area...so if your handheld cannot do anything well... it's most likely broken or a dud, period, and the problem has little to do with the antenna (or maybe it's internally disconnected).

March it back to WM, and have them fire up another of the same model. If they both suck the same, get your money back and run away!

Don S/V ILLusion · Aug 2, 2010

Jeff Bacon said:
Don:

To clarify, if VHF HH antennas are a compromise because they have to cover a broad range of VHF frequencies, wouldn't an antenna that is asked to cover an even broader range of frequencies (AM/FM, FRS, Aviation, VHF ) even be more of a compromise ?

On the flip side then, what makes one HH better than another if the antenna is only a fraction of the problem.

Thanks ! ......... Jeff

Think of the radio as a means of tuning a wide range of frequencies and separating a multitude of signals on those frequencies. A good receiver capable of discriminating all signals within a limited freq range is what you want. What you have is a barn door (bad metaphor for a very wide receiver) with no means of filtering between everything entering. The antenna only serves to conduct those signals - it's not normally the problem on a receiver. The barn door is the problem. An over-simplification is that it cannot discriminate effectively, the result being a weak receiver.

You would be better served with a purpose-built HH which also has provision for, in order of preference, 1. an external antenna connection or 2. a replacement telescoping whip antenna in lieu of the so-called "rubber duck" with which these things are typically sold.

I won't discuss particular brands or types as preferable as my opinion is just that but if you want some knowledgeable advice where to go from here, there is a ham/ssb/marine radio forum on this board under the Social Group tab where there are some experienced radio guys.

FourPoints · Aug 3, 2010

Don S/V ILLusion said:
First, any antenna can be resonant only on a specific frequency.

as far as a whip or rubber duck style antenna, you are correct. HOWEVER, there is a new breed of antennas (that are gaining popularity in cell phones) that are tuned to be simultaneously resonant in multiple frequencies.

http://en.wikipedia.org/wiki/Fractal_antenna

Don S/V ILLusion said:
If you're still with me, it will always help to use a resonant antenna not because the receiver requires it but the transmitter efficiency and therefore it's range will be greater.

So, not hearing much usually isn't the antenna which as stated is more important for the transmitter end of the HH.

actually that is not correct. An antenna is tuned for a particular frequency, and that applies equally to both the transmit and the receive functions. You can hook up any antenna to any receiver and receive some signal, but if the antenna is not tuned for the wavelength of the frequency that you want to receive, the signal reaching the receiver will be MUCH less that that of a similar receiver with a properly tuned antenna.

Receivers all have a measurement called receive sensitivity, depending on the quality of the receiver this can easily be 20dB different between a high quality receiver, and a cheap one. this number represents the minimum signal strength that the receiver has to receive to be able to understand and decipher the signal and turn it into something meaningful. When dealing with RF, everything is measures in dB (decibels), and when dealing with signal strengths, every 3dB change is a exponential double, or half of the signal strength.

for example on the transmit side 30dB equals 1W (watt) but 27dB equals .5W or 500mW, and 24dB equals 250mW. (technically when referring to signal strengths, there is a m after the dB indicating it's relation to milliwatts, I omitted this for ease of reading, so everything above would actually read dBm)

Receive numbers are typically measured in negative decibels, and as an example, your laptop wifi transmits with a typical power of around 80mW, or 19dBm, and when the signal is received from across the room at your wifi router, the signal the receiver in the router is seen at around -50dBm, or from 1-2 rooms away, around -80dBm.

The receive sensitivity of a receiver indicates what the weakest signal it can decode. a cheap wifi device has a receive sensitivity of around -85dB, and a typical wifi router has a receive sensitivity of around -90dBm, but a high end wifi radio has a receive sensitivity of around -105dBm

Your cell phones have a typical receive sensitivity of around -180dBm (effective only because they have dedicated frequencies to operate on).

As you now now that a change of 3dBm equates to a double, or halving of power, you can understand that the receive sensitivity of a radio can be just as important as the antenna attached to it. Combining a non tuned antenna with a cheap receiver means you are reducing the signal brought in by the antenna by anywhere from 3 to 10dB, and trying to pick up the weak signal with a radio that needs a hearing aid to hear it.

my recommendation, buy a better single purpose radio for anything you plan to rely on, and if you want something that does multi-band operations, keep it mostly for your own amusement.

sullyj020 · Aug 3, 2010

Do you have a Squelch control on the radio? if you do, turn it. if its off you will not receive anything or very little.

FourPoints · Aug 3, 2010

Jeff Bacon said:
Seriously ? Are you kidding ?

lol, I guess there is nothing wrong with making sure you covered the basics...

Brian D · Aug 4, 2010

Multi Mode, Multi Band radios are getting popular. They were in the 80's and still are. Look at the Ham community with their VHF/UHF Multi Mode, Multi Band radios. The key to any communications is the means of getting the signal out. I don't think there is a major issue with the radio, I think the antenna (as touched on by many) is the culprit.

Look at the band you are trying to listen to:

FM Broadcast 88 ~ 108 MHz
Aircraft 108 ~ 135.95 MHz
Marine 156 ~ 174 MHz

You are trying to fit signals in a range of 86 MHz. Now, as mentioned before, just about anything can be used to receive a signal, if the signal is strong enough. I have used paper clips (as mentioned before) on a HP Spectrum Analyzer to show an FM broadcast and cellular activity. So it can be done. But to be done right, the antenna must be tuned to the center of the band you want to operate.

I would try and get an antenna specifically designed for the Marine VHF band. You can even build one if you know the formulae. But purchasing one would be better.

One thing is to connect to your mast mounted antenna to see if you hear the same radio communications. Don't use Coast Guard or Wx, they are transmitting on higher power with taller antennas. Find some communications on like channel 22 or 68 and listen on the big radio, then try the little radio and see if you get the same results. If not, get a new handheld.

BarryL · Aug 4, 2010

Hello,

I have the same radio. It *should* work OK. I bought one, it worked for a day and then the antenna got flaky - if I pressed the antenna to the side it would work, let go and no reception. Back to the store for a new one - I tested it in the store and it had the same problem. Tried one more and it worked fine.

I have used it casually for a year and its still working. I am very careful to not bend the antenna. Note that the antenna on the VHF250 (multiband) is very different than on the VHF150 (just VHF and weather).

Last comment - you do need to adjust the squelch to receive am / fm

Barry

Dan Johnson · Aug 4, 2010

Jeff...

from personal past flying experience 'bout the only time you hear "frequent" aviation talk is on the tower frequency around an airport or near a control center. Otherwise there's very little "chatter" on the aviation channels as they keep any communication to the briefest possible.