Can anyone tell me about this antenna I have? I've never seen one like it and don't know who made it. I'm using it with an R.V.R TEX30LCD exciter.
I've set up a temp drive in movie and this is the transmitter we have. It can do 30 watts, but found that even 16 watts caused all sorts of nasty noises in my audio gear. Backing it down to 0.9 watts does the trick and covers more than I need.
But what about this antenna? I don't know the type. Should it be mounted horizontally like a Yagi? Why does the driven element look like it's grounded at one end? It seems to work well, just curios about how it's supposed to be used.
Note: In the first picture were you see the letter D in the tube that's a sticker that says DOWN. I have used it with that down, but it didn't seem to matter.
I've set up a temp drive in movie and this is the transmitter we have. It can do 30 watts, but found that even 16 watts caused all sorts of nasty noises in my audio gear. Backing it down to 0.9 watts does the trick and covers more than I need.
But what about this antenna? I don't know the type. Should it be mounted horizontally like a Yagi? Why does the driven element look like it's grounded at one end? It seems to work well, just curios about how it's supposed to be used.
Note: In the first picture were you see the letter D in the tube that's a sticker that says DOWN. I have used it with that down, but it didn't seem to matter.
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It apprears that that clamp block is possibly for tuning the SWR for the actual transmitted frequency.
It is a single driven element yagi.
The driven element can be either vertical or horizontal.
Loosten the set screw to tune the operating frequency for lowest reflected power.
High reflected power can cause all sorts of nasties.
The driven element can be either vertical or horizontal.
Loosten the set screw to tune the operating frequency for lowest reflected power.
High reflected power can cause all sorts of nasties.
Motorola spec is 10% reflected maximum.
I try to keep it under 5%.
This stuff is my jam for about 20 years now.
I try to keep it under 5%.
This stuff is my jam for about 20 years now.
You need to strike a -18db line and that is your passband on the antenna.
Along the bottom is the frequency in MHz.
So long as your TX frequency falls within the -18db passband you'll be fine.
Make sure you have good quality coaxial 50R cable.
I tend to use LMR400 more and more, especially at these low frequencies.
Look for coax that is at least 90% shielded or something like a dual 85% or a foil shield plus a braided shield.
Keep the antenna away from sensitive unshielded electronics.
It will radiate omnidirectionally in the near field.
PM me and we can have a more in depth chat if you'd like.
Along the bottom is the frequency in MHz.
So long as your TX frequency falls within the -18db passband you'll be fine.
Make sure you have good quality coaxial 50R cable.
I tend to use LMR400 more and more, especially at these low frequencies.
Look for coax that is at least 90% shielded or something like a dual 85% or a foil shield plus a braided shield.
Keep the antenna away from sensitive unshielded electronics.
It will radiate omnidirectionally in the near field.
PM me and we can have a more in depth chat if you'd like.
We used to cover the entire city of Haarlem with one of those transmitters (*), so I'm not surprised you had to reduce power. FM transmitting antennas are usually vertically polarized, at least on this side of the Atlantic, so I expect the driven element has to be mounted vertically.
(*) with an array of two vertically polarized dipoles at 34 m height, and about 2/3 of the transmitter power ending up in the antenna
(*) with an array of two vertically polarized dipoles at 34 m height, and about 2/3 of the transmitter power ending up in the antenna
Yes, it was a "Duh!" moment. 16 watts of RF power at no more than 2.5 meters from the audio rack. No wonder it buzzed like a banshee. 😀
You used the lovely Italian R.V.R transmitter?
You used the lovely Italian R.V.R transmitter?
Consumer equipment should withstand 3V/m and a lot of HiFi does not manage this, even though it is CE marked
10W at 144 MHz at 2.5m is closer to 10V/m
10W at 144 MHz at 2.5m is closer to 10V/m
CE only stands fir China Export.
That is quite regularly mistaken for ETL or UL listing.
CE quite literally means nothing other than it came from China.
That is quite regularly mistaken for ETL or UL listing.
CE quite literally means nothing other than it came from China.
If they can see the screen, a part-Watt is ample signal. You could even get away with boiled pasta for antenna. A 10+Watt transmitter cut-back to 1 Watt is not gonna die at any SWR.
Get the RF away from the audio (strict segregation in radio stations). Cliplead the transmitter to a coathanger tied to a tree with poly rope. SS preamp line-out will drive 50 feet of coax further up the audio band than any car-radio can deliver.
Get the RF away from the audio (strict segregation in radio stations). Cliplead the transmitter to a coathanger tied to a tree with poly rope. SS preamp line-out will drive 50 feet of coax further up the audio band than any car-radio can deliver.
You mean this CE mark? CE marking | Internal Market, Industry, Entrepreneurship and SMEs
"The letters ‘CE’ appear on many products traded on the extended Single Market in the European Economic Area (EEA). They signify that products sold in the EEA have been assessed to meet high safety, health, and environmental protection requirements. When you buy a new phone, a teddy bear, or a TV within the EEA, you can find the CE mark on them. CE marking also supports fair competition by holding all companies accountable to the same rules."
I live in the EU, more often than not, I am disgusted at the low quality products we customers have to be contented with. The CE mark means absolutely nothing. Even in "leftist leaning EU", laws favour the market, business and business-persons. Customers come the very last, if at all! I have experienced this first hand.
There are two very similar CE marks, one that means that the manufacturer believes and guarantees that the product complies with all the European standards (including safety standards and a bunch of electromagnetic compatibility standards) and the other means China export. The second one is just a trick the Chinese came up with to more easily sell stuff that doesn't comply with the European standards.
Pano, yes, we used to use the very same Italian transmitter model.
Pano, yes, we used to use the very same Italian transmitter model.
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The "China Export" thing is a urban myth that we often use to ridicule import devices with CE stickers that are blatantly non-compliant . They come mainly from online sales and bargain shops that have found "alternative" import routes to the EU. Those unscrupolous sellers are exploiting a loophole in the current EU sanctioning system. As a general rule, if a product has a CE mark but the manufacturer is unrecognizable, the CE mark is fake, it is "China Export", even though I believe the worst offenders now are mainly from other countries with lower quality standards and business ethics.
I have done pirate radio long ago, then I did use a J antenna who radiate in a disc and have 3 dB gain some says even 6dB.
I had a fm transmitter of high quality, I had 100 watts, but never problems with buzzing audio equipment, when it does there are much harmonics present, also parasitair oscillatings in a fm transmittor does that.
Here is the pcb, did make it with the old Ultiboard. with dipswitches, I can do 80 to 120 Mhz. The pcb is from 1983 so pretty old, but still works, I did some experiments with it in past so it looks bad on the oscillator pcb, test using feedback for a lineair modulator to the stereo coder using a demodulator.
But Hee now I am here, I have a TOm Tom in then closed here, I did hear suddenly it is on, how can a tom tom go on on it,s own, now we have ot about rf power, maybe there is here around mine house a guy playing with it causing the tom tom to go on. The pc the same, when in sleep, it wakes up all the time on it,s own.
If it is RF cause I take steps.
regards
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