balacleigh
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Order of wiring etc
Dear All,
Could anyone guide me please ? What is the order to connect the following - 2 Kenwood low pass filters, an SWR metre, an ATU and a linear amplifier. One of the Kenwood filters would go between the radio and linear and the other after the linear.
The antenna is reasonably well tuned
Am mindful that getting the order wrong could be bad news.
Many Thanks.
Many thanks in advance
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20/Nov/2011, 7:56 pm
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yamanx1
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Re: Order of wiring etc
Radio
Amplifier
Meter
ATU
Filter(s)
What equipment are you using?
Doers the ATU have a built in meter or are you using a seperate meter and ATU?
Size of the amplifier? Does the ATU cope with the output?
Through what aerials and foor which bands?
Loads of questions
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By all means think yourself big, but never think others small.... R.F.Scott |
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21/Nov/2011, 8:28 am
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Hot Fusion
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Re: Order of wiring etc
And what sort of linear?
If it is a valve unit, you really needn't worry about the filter at all.
Just to be different to Dave, I'd use the SWR meter to ensure the antenna is properly tuned, then remove it completely.
No need for the tuner either, as long as the antenna presents a good match, less than 1.5:1 or so.
Then I'd go:
Radio
Linear amp
Filter
If you need the tuner to bring the SWR under control, then go for Daves recommendation, but be sure the tuner can handle the amp's power!
EDIT:
Forgot to mention, you don't need 2 filters, just the one right before the antenna.
Last edited by Hot Fusion, 21/Nov/2011, 9:13 pm
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Andy - FB107
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21/Nov/2011, 9:12 pm
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balacleigh
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Re: Order of wiring etc
This is a very belated response to say thank you for the responses !
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17/Oct/2012, 7:31 pm
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29fb380
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Re: Order of wiring etc
do not run two low pass filters. run one after the ATU or amp if not using an ATU.
This is because of a quote from 2007 rsgb handbook chapter 7 hftx page 15/46
the desire to achieve high levels of signal purity may tempt constructors to place additional low-pass filters between cascaded broad-band amplifiers, but this practice will almost certainly result in spurious VHF osscilations. These occur when the input circuit resonates at the same frequency as the output circuit, ie when the filter acts as a short circuit between the amplifier input and output circuits. Low pass filters should only be amployed at the end of an amplifier chain. If it is essential to add an external amplifier to an exciter which already incorporates a lowpass filter, it is important either to use a resistive matching pad between the exciter and the amplifier, or modify the output low-pass filter to ensure that it has a different characteristic to the input filter im tired of typing
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19/Oct/2012, 3:52 pm
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yamanx1
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Re: Order of wiring etc
Interesting, I think I'll do some serious investigation, cheers for that.
I suppose this would be right for radios or PA's with LPF built in? And at what level I wonder?
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19/Oct/2012, 7:37 pm
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29fb380
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Re: Order of wiring etc
it does sound pretty vague but i take it to mean that if you use two identical low pass filters as OP has, you could run in to trouble. i don't care what it says i'm not about to pull the low pass tuning slug in my 2970n2 lol
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19/Oct/2012, 8:40 pm
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balacleigh
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Re: Order of wiring etc
Thanks for the informed comments - you may be interested to know that Kenwood Low Pass Filter (LF30A) instructions specifically address the use of 2 Kenwood low pass filters.
See the link :
http://servicedocs.com/ARTIKELEN/7200228260001.PDF
Regards
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23/Oct/2012, 8:03 pm
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John193
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Re: Order of wiring etc
LOL I did love this one. There's a LP filter in the mixer the driver and pwramp unit of your transmitter. Then theres another two pass filters in your linear. The RSGB quote revolves mainly around the parasitic oscilations between equipment filters and lengths of coax which in itself is a tuned circuit. This was prevelent when Hams had a separate exciter and amp, but at most shack coax lengths this parasitic is way up in the uhf band anyway and very low order.My advice would be to test your output signal with a remote reciever if its clean leave it alone if not find out why and then fix it. The more links in the chain the bigger the chance of a weak one. John193
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19/Feb/2013, 2:19 pm
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balacleigh
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Re: Order of wiring etc
Great advice John. Thank you and sorry for the late reply. I intend to earth all the equipment and test the 2nd etc harmonic with one and 2 filters. They are both Kenwood and the length of the connections are relatively short.
Regards
Last edited by balacleigh, 14/Jul/2013, 6:54 am
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14/Jul/2013, 6:53 am
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