Thank you, Ramsey!

Mallette · #1 12-22-2008, 12:18 PM

I could have re-soldered connections until the cows came home and not found the reversed resistors you corrected in my FM30B. Your service and support are top knotch!

Two notes:
1. Lock still does not light...but it sounds great so I don't really care.
2. When I first retuned the hum was still there. It was only by gradually moving up the dial that I found that hum starts around 102 and increases as you as you go down, decreases as you go up. I don't know if this is generally true or perhaps something in my home or area, but if it is generally true you might want to make note of this to users.

Thanks again for a great job...I've recommended this unit as the very best and lowest cost whole-house and grounds high quality audio distribution system available. My wife loves it, because it is simple and goof proof. You should direct more advertising to audiophile circles.

Regards,
Dave

Mallette · #2 12-26-2008, 11:39 AM

Hum is still present, but at a low level. It is not really noticable when there is music, but it would be nice to be able to get rid of it.

Anyone know what sources produce hum on an FM30B?

Dave

meldar_b · #3 12-27-2008, 06:35 AM

I don't have this Ramsey FM transmitter

But from past transmitters that I have used from Ramsey it always helps to put your FM transmitter in a metal enclosure. This will keep out any unwanted rfi from getting back into your unit. Also use some ferrite cores on all your hookup cables Audio, Power, external antenna.

see my ramsey case mod page for my FM25B I did this case mod years ago

still works great today

http://www.geocities.com/meldar_b/casemod2.html

Mallette · #4 12-27-2008, 01:55 PM

I'll give it a try as it sounds rational. Part is easy, the metal enclosure I am going to have to hunt around.

Think heavy foil might do it?

Dave

meldar_b · #5 12-28-2008, 06:02 AM

NO,

I have already been down that street and it does not work at all. The foil has a real bad connection to the the ground of your transmitter and will cause a horrible static on your broadcast.

Quote:

Originally Posted by Mallette

I'll give it a try as it sounds rational. Part is easy, the metal enclosure I am going to have to hunt around.

Think heavy foil might do it?

Dave

RDEngineer · #6 12-29-2008, 08:34 AM

The FM30 is in a metal case. THe hum problem has been fixed with a set of shielding tabs on the case bottom and a ferrite filter on the power cord. If you reciently purchased the unit it has the fix. if it's more than about 1 1/2 years old it may not have the fix. A retrofit and installation instructions are available for about $5 from our sales department. This will fix the most of the hum. Yea there is a chance there will be a small amount of hum still there but it will be so far down unless you turn up the volume of your receiver you probably won't hear it. If you are using an external antenna you shouldn't have a llot of hum. The whip can cause some hum on the older units.

meldar_b · #7 12-29-2008, 10:20 AM

Quote:

Originally Posted by RDEngineer

THe hum problem has been fixed with a set of shielding tabs on the case bottom and a ferrite filter on the power cord. A retrofit and installation instructions are available for about $5 from our sales department.

Awesome!

Can this retrofit be a added to the FM25B?

Mallette · #8 12-29-2008, 11:37 AM

I bought mine about 4 months ago from Hobbytron and it does not have any ferrite on the power supply. Just to confirm, is the power supply a 15v, 1A GobeTek? I have so many it's possible it's been switched.

Also, the whip is not an external antenna? What would an external antenna be, unless you simply mean outside the house. I have some BNC adapters I could use to place the whip farther from the unit. Would that help?

Perhaps I should order the kit. At 5.00 I suspect that is well worth not having to make a trip to Fry's or somewhere.

The sound quality is excellent, but that makes the hum all the more maddening to an audiophile.

Dave

RDEngineer · #9 12-29-2008, 12:37 PM

The FM30B is normally supplied with a whip antenna that attaches to the BNC antenna connector. By external antenna I mean something other than the whip away from the unit. If your unit did not come with 6 small spring clips and a ferrite filter then you got a pre mod unit from old stock at Hobbytron. Otherwise it is possible they removed them, although I would think this is unlikly, but anything is possible. We pack them with the shielding kits. Also the assembly instructions include installation instructions. If yours had no mention of installing them then you got an old stock kit. If you bought it from Hobbytron assembled then they bought it from us as a kit and then put it together without the shielding. We DO NOT assemble any FM30B's for anyone. Installation of the mod will clear up your hum with the whip antenna. Call our sales at 585-924-4560 and ask for the shieling kit for the FM30. I don't know what the stock number is but they will be able to help you.

RDEngineer · #10 12-29-2008, 04:30 PM

To answer the FM25 question.. The FM25 is in a plastic case so the only shielding you can do ,short of putting it in a metal case or trying to wrap foil around it, is a ferrite on the power cord, and audio lines. Often simply moving the lines around will help. Using an antenna moved away from the unit will also help if there is a really big problem. No matter what the unit it is important to keep in mind that these are hobby products. It will not be possible to get the same quality of sound as you get from the commercial stations but for most purposes it is really great sounding.

The reason the FM30 costs more than the FM25 is the fact that it has more filtering and processing of the audio and RF signals. If you check closely you will find that the main engine that generates the signal is the same but the user interface and the above mentioned items have been changed for some improvement. Some members say that by simply changing the power supply they have eliminated hum and this is possibly true but it is not necessarily because it is a better supply. The power sypply system in the units is adequately filtered and usually the hum is caused by RF leakage into the unit from the antenna. THat's why the shielding retrofit fixes the problem. It just happens that the new supply has a little better filtering in the RF area and also possibly the power cord is longer, shorter or in a different orientation. Try rearranging things before you buy a new supply, you may be supprised with the results.