Hello
I designed a 7W VHF RF power amplifier successfully it's take the signal from PLL 1W transmitter i measured the output power by my rf swr/ Watt Meter, itsi show's 6 watt forward and about 1watt reversed from the Antenna. And i received the signal from about 5KM
But the i designed another stage 40watt
The power meter shows 40 watt forward power and 7 watt reversed power fron antenna.
But when i test the signal outside , i recived it at maximum distance at 6km
Why there is no increase in distance ?
What's wrong ??

* I test the signal in open space no objects between me and the transmitter antenna
I hope you can help me with this

 

What is the frequency? What type and length of feed line? Height of antenna.

What is specs on swr or power meter? Have you got a 40 watt dummy load?

Have you tried to tune for zero return power?

Is the terrain multi-soiled? Rocks, lakes? mud fields?

 

Maybe nothing. VHF propagation is influenced by a number of things that change on a day to day basis. You did not mention the part of the spectrum you are working with, but the guys going for distance records at frequencies in excess of 400 GHz., use rifle scopes to aim their VERY directional antennas at the receiver on cool dry mornings at dawn or shortly thereafter.

Also -- tell us what kind of antenna you have.

The return loss of your two systems is between 7.6 dB and 7.8 dB. For better performance you want a much higher value. Something in the range of 30 dB would be better. At lower values you are seriously stressing your final output stage.

As any ham will tell you, you get far more bang for the buck paying attention to the feedline, matching networks, and antenna gain. Only after you have taken care of those things do you boost your output power. Nothing hurts an amplifier more than reflected power.

 

What is the frequency? What type and length of feed line? Height of antenna.

What is specs on swr or power meter? Have you got a 40 watt dummy load?

Have you tried to tune for zero return power?

Is the terrain multi-soiled? Rocks, lakes? mud fields?

The frequency is 100Mhz
50ohm coaxial cable contacted .to dipole antenna 10 meter length
I tried to tune the circuit to have zero return power but I couldn't

 

The frequency is 100Mhz
50ohm coaxial cable contacted .to dipole antenna 10 meter length
I tried to tune the circuit to have zero return power but I couldn't

Why are you transmitting on this frequency?

 

The frequency is 100Mhz
50ohm coaxial cable contacted .to dipole antenna 10 meter length
I tried to tune the circuit to have zero return power but I couldn't

Can you explain why you picked the middle of the FM broadcast band? AFAIK it is illegal for you to transmit at ANY power level on that frequency. Stop doing it.
10M antenna won't work very well at that frequency. It should be more like 1.5 meters for a half-wave dipole. I'm not sure you can tune away that much of a mismatch. A dipole is not what I would call a directional antenna, and they are not typically used on VHF channels.

 

Hello,

Using that kind of power on that frequency might get you into trouble.
In holland when you get caught using such transmitter a fine between 1200 and 45000 Euro can be given.
Also all equipment will be taken, also that whatever is connected to the transmitter.

Bertus

 

I think he is trying to jam a religious, rock music or classical music FM radio station. In addition to the fine for causing interference he will go to jail for being racist.

When I built my little FM transmitter my dial was full of stations so I picked the frequency of a foreign language station and I was lucky that I did not get caught. I never used the transmitter again. The next day my neighbour saw the RF cops on my street in a van with antennas on top.

 

... he will go to jail for being racist.
...

A bit of a stretch, assuming facts not in evidence.

 

Having RF cops on your street is not the same as an RF cop ringing your doorbell. Aaaaaahhhh....the thrills of my mis-spent youth!

 

Having RF cops on your street is not the same as an RF cop ringing your doorbell. Aaaaaahhhh....the thrills of my mis-spent youth!

Except they never do it in person:
Step 1: LOI - Letter of Inquiry. This means they are investigating and gathering information
Step 2: NAL - Notice of Apparent Liability for Forfeiture. This is their proposal for what you need to do as a result of their investigation. You can fight them in court, but you will most likely lose.
Ignoring either of those two missives is generally speaking what brings heavy weight.

 

In this case, he showed up while we were transmitting. He just wanted us off the air, which is the result he obtained as soon as the doorbell rang.

 

That is a strange frequency for 40 watts. Are you in the outback? How did you "tune" the system?

A dummy antenna will verify the transmitter, the feed line and the meter.

Normally, one would think antenna. But with 40 watts......at 6 km......even with mis-match......you should see difference.

So.........I would check power out with a flat load.