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Watt meter
- Thread starter jdchet
- Start date
Mfj-870 I've owned a couple and are good enough but better than any of the dosy style meters. It has pep reading but isn't true pep like the ones you pay a tad more for.
I've been pleasantly pleased with the Daiwa cn-901hp but it's a hair over what you're wanting to spend.
I've been pleasantly pleased with the Daiwa cn-901hp but it's a hair over what you're wanting to spend.
I too can recommend the Daiwa CN-901. Decent meter with peak reading. It's what I use.
I use the DIAMOND antenna meters they have AVG and PEP . I cant say for sure if they are true peak reading or not but I have had 2 of the SX 200,s and now use the SX-100 it works for all of my needs now .
The Diamond meters are NOT true peak reading. No meter is unless it has a powered circuit and the only power the Diamond meters use is for the meter lamp. I have had a Diamond SX-1000 for many years and it is indeed a good meter.
Peak reading RF wattmeters come in two basic varieties. Passive and Active.
Passive is most common and cheaper to provide. A capacitor is added to the meter circuit. It gets charged up to the peak power amplitude of the transmit signal, and discharges into the meter's coil to hold the needle of the meter up during the "valleys" . between the peaks. This method tends to be most accurate on higher power ranges of the meter, and least accurate at the lowest power ranges. The reason is simple. The higher the transmit power, the more energy is available to charge up that capacitor.
An "active" peak reading meter uses the capacitor trick, charging it up to the highest peak amplitude of the transmit signal. But rather than discharging the capacitor directly into the meter coil, a current-amplifier circuit allows the capacitor to discharge more slowly, and hold up the meter needle for longer. Drawback is that this amplifier circuit requires a source of power for that amplifier circuit. The passive type won't need a power source, except maybe to light up the meter face.
The ultimate test for a peak-reading meter is to turn up the mike gain and slap a pencil against the front of the mike. If the meter shows the same reading you get from a "helllooo", it's a true peak-reading meter.
The problem here is that making that "hang" time too long makes the meter useless for making peak adjustments to a radio or amplifier. The long "hang" delay for the needle to drop hides the up-and-down effect of tuning adjustments.
We use an active peak adapter with our Bird wattmeters. Uses a 9-Volt battery. We use rechargeables, and charge them once a week. The 'hang' time is adjustable, and I set it to drop back a bit fast. Our meters fall back too fast to show lab-grade "true peak" level. Makes them more useful as a repair-bench tool so you can see the effect from turning an adjustment. Drawback is that PEP readings will be a few percent below that "true" peak you get from the long hang time. A customer never complains if his wattmeter at home reads just a little more than the reading we recorded on his repair bill.
73
Passive is most common and cheaper to provide. A capacitor is added to the meter circuit. It gets charged up to the peak power amplitude of the transmit signal, and discharges into the meter's coil to hold the needle of the meter up during the "valleys" . between the peaks. This method tends to be most accurate on higher power ranges of the meter, and least accurate at the lowest power ranges. The reason is simple. The higher the transmit power, the more energy is available to charge up that capacitor.
An "active" peak reading meter uses the capacitor trick, charging it up to the highest peak amplitude of the transmit signal. But rather than discharging the capacitor directly into the meter coil, a current-amplifier circuit allows the capacitor to discharge more slowly, and hold up the meter needle for longer. Drawback is that this amplifier circuit requires a source of power for that amplifier circuit. The passive type won't need a power source, except maybe to light up the meter face.
The ultimate test for a peak-reading meter is to turn up the mike gain and slap a pencil against the front of the mike. If the meter shows the same reading you get from a "helllooo", it's a true peak-reading meter.
The problem here is that making that "hang" time too long makes the meter useless for making peak adjustments to a radio or amplifier. The long "hang" delay for the needle to drop hides the up-and-down effect of tuning adjustments.
We use an active peak adapter with our Bird wattmeters. Uses a 9-Volt battery. We use rechargeables, and charge them once a week. The 'hang' time is adjustable, and I set it to drop back a bit fast. Our meters fall back too fast to show lab-grade "true peak" level. Makes them more useful as a repair-bench tool so you can see the effect from turning an adjustment. Drawback is that PEP readings will be a few percent below that "true" peak you get from the long hang time. A customer never complains if his wattmeter at home reads just a little more than the reading we recorded on his repair bill.
73
I thank everyone for their input. I've pretty much decided on the MFJ 815D. I think at that price point it will give me what I'm looking for without breaking the bank. The deciding factor had alot to do with Nomad's above post on how true peak reading meters work and this one seems to fill the bill.
https://www.dxengineering.com/parts/mfj-815d?rrec=true
JD
https://www.dxengineering.com/parts/mfj-815d?rrec=true
JD
I like my MFJ 870 meter, although it is too large for me at least in the mobile. It is good for the house. Seems to be a little stingy on max power reading. Seems to be great for reading SWRs and reflected power.
My only complaint is the knobs to switch power settings, cal, swr are awful. I wound up just pulling them off and use a small screwdriver instead.
Once I get a base station going again I may get a 815.
My only complaint is the knobs to switch power settings, cal, swr are awful. I wound up just pulling them off and use a small screwdriver instead.
Once I get a base station going again I may get a 815.