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NLC

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On 2/4/2022 at 2:42 PM, canadianchristmas said:

I'm not Kc, but I'll be the first to tell you nooooooooo.

Don't use that.

Firstly it is a 7w transmitter, that is way too much power for what we are doing, you could get more range than you ever anticipated and could cause interference (more on that later).

Furthermore if you are using that much power with a rubber duck antenna, or some other small telescopic antenna  you are likely to damage the transmitter at some point due to poor SWR performance with that high of a wattage. Basically you will likely have some of that power feeding back into the transmitter. A good antenna is always key, like a nice well tuned dipole.

Another note is that a lot of those "transmitters on a chip" usually use crappy chips. I can't speak for the BH1415 specifically as I don't personally know about that one..

But a lot of them are crap and best to be avoided.

The one you linked looks like a clone of the CZH-7C, which is a POS, that can cause a lot of spurious harmonics on the band, interfering with other frequencies and bands that you didn't intend.

 

For my shows I personally use a EDM transmitter. https://www.edmdesign.com/

I heard recently on DIYC that their order page is down right now due to not having any enclosures but apparently they are still taking orders over email.

Another pick would be one of the PCS electronics transmitter (exciter units) like this one: https://www.pcs-electronics.com/shop/fm-transmitters/fm-transmitter-kits/maxpro8015-25-15w-25w-superbass-fm-exciter/

Keep in mind that a lot of the PCS kits can run up to 15w so you will obviously want to turn that down to around 100mw-ish.

Another nice clean kit, would be the Dutch RF shop exciter..

But be warned when you start to get into more "professional" level transmitter/exciter units you will likely need a stereo generator to drive an MPX signal to it, which adds another layer of complexity and could introduce a noticeable delay or cause over modulation, if it isn't configured properly. But that is a topic for another time. 

I am just rambling at this point lol. I like broadcast and radio stuff.
 

Thank you for your input. So much to learn. Could you give me a ballpark amount that I could be spending? I need to give the board of our Church a approximate cost of what I am planning so this would need to be in the budget. If they approve, I get someone with a lot more knowledge then me to do the buying.

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2 hours ago, NLC said:

Thank you for your input. So much to learn. Could you give me a ballpark amount that I could be spending? I need to give the board of our Church a approximate cost of what I am planning so this would need to be in the budget. If they approve, I get someone with a lot more knowledge then me to do the buying.

I'd say your probably looking at around $150-200 for a decent transmitter setup.

Some of the ideas I listed in my original posts were overkill, I just enjoy radio.

 

Personally if I were you, I'd try to get in contact with EDM.

their sales page is down right now apparently due to not being able to get enclosures for the transmitters until sometime later this year. This thread on doityourselfchristmas talks about it, that is what I was referencing in my earlier post.

If you can live without the metal case on your transmitter, or wait awhile EDM would be your best bet. Their email is "sales@edmdesign.com". I'd ask what their current inventory and pricing is like at the moment.

One word of note though about the EDM transmitters, is that you need to solder the power connector on yourself due to legalities, although it is very easy. Also be sure to ask for the rubber duck antenna in your order if you don't plan on using a better external antenna.

This would be what I would personally choose.

 

If you don't want to go the EDM route, I'd go with the CZH-05B, also known as signstek, along with a bunch of other names. They are really all the kind've the same. You can find these on amazon, ebay, aliexpress, etc...

It is a chinese transmitter on a chip that can output a between 100-500mw which should be more than enough for most, if not everyone.

But as I said in my earlier posts if you go this route, be sure to use some kind of low pass filter with it, just to get rid of any potential spurs.

I personally like this one from dutch RF, I linked the pre-soldered PCB, but you could also get the kit version and wind the coils yourself on drill bits if you feel confident in your abilities. Keep in mind that you will still have to solder BNC connections on the inputs and outputs.

There is also this one from progressive concepts which comes as a pre-assembled unit, just be sure to choose the "w/BNC" option as you will need the version with BNC connectors. The nice thing about this one is that it's all completely self contained, shielded, and ready to go. But it is kinda pricey for what it is.

 

Anyways hope this helps.

Edited by canadianchristmas
clarification.
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With any low power transmitter: Get it as close to the users as you can. Why wast range on open spaces with no radio.

K6CCC has his inside the post WITH THE ANTENNA OUTSIDE the post (not the rubber ducky supplied), right near the curb. 👍

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57 minutes ago, TheDucks said:

K6CCC has his inside the post WITH THE ANTENNA OUTSIDE the post (not the rubber ducky supplied), right near the curb. 👍

Correct.  I have two brick columns right at the sidewalk on either side of where there will be a walkway.  The FM transmitter is inside one of the columns.  Since the columns are brick and concrete with lots of rebar, it would work very poorly with the antenna inside the column, so I built a vertical dipole antenna that is mounted onto the column.  This page has some information and photos about it:  http://www.newburghlights.org/Technical.html#Antenna

 

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I have both the EDM and a C50Z. I got the EDM first so that I could use the radio data feature. When I bought the C50Z as a backup, one season I tried it and got clearer reception than with the EDM. No clue why and I don't have an SWR meter. LOL, I should send it to Jim as he's one of the experts on Radio.

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1 hour ago, dgrant said:

I have both the EDM and a C50Z. I got the EDM first so that I could use the radio data feature. When I bought the C50Z as a backup, one season I tried it and got clearer reception than with the EDM. No clue why and I don't have an SWR meter. LOL, I should send it to Jim as he's one of the experts on Radio.

I'd check your power switch inside the EDM.

It has a low and high power setting, I think high power is 500mw although (I could be wrong about that). And low power is either 10mw or 100mw. Can't remember.

 

As for SWR it shouldn't make that much of a difference on such a low power level. I was more referring to SWR in regards to reflected power when using 7 watts on a rubber duck antenna.

Having that much power going through a rubber duck would likely have a fair bit of reflected power that would heat up and cook the transmitter over time.

But for anything under 3w I don't think it should matter all that much.

So using a rubber duck or even a wire with an EDM or CZH-05B shouldn't matter, however it will effect how far you are able to transmit

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High and low on the EDM is (as I recall) 100 and 10 mWatt

SWR and power have no relationship.

Commercial two way radio users and Hams have been using 3 - 7 watt transmitters with rubber ducky antennas for decades.  Works as well as can be expected for a crappy antenna.

SWR tolerance depends on the design of the transmitter.  The CZH05b and CZE05b transmitters have no protection and the docs say that transmitting into no antenna will instantly kill the final RF amplifier.  The EDM docs says that it can take an infinite SWR without damage.  Take both of those for whatever they are worth.

 

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7 minutes ago, dgrant said:

I do use a rubber duck antenna but it was made for 2M ham

That is not the best (optimum 1/4 wave for the 88-108MHz range). Each driven, radiating element should be tuned to the frequency it is operated at.  A whip (ducky) is a 1/4 wave. (the ground plane is the other 1/4 wave of the Dipole) .  An SWR meter, is a tool to help you adjust the 'electrical length' so that all the RF gets to the antenna.  A old VHF rooftop antenna, would also direct more of the power to the front.  FM band is between the old Ch6 and Ch 7

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