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AB3FN

Joined: Tue, Jun 5th 2007, 14:11 Roles: N/A Moderates: N/A

Latest Topics

Topic Created Posts Views Last Activity
question about interference on 70 cm band Feb 11th, 08:07 2 531 on 11/2/20
calculation of PEP ? Mar 20th 2019, 10:04 5 1,740 on 27/3/19
question re FTDX 1200 clock Oct 26th 2017, 12:47 1 1,818 on 26/10/17
CW for stroke victim ? Jun 17th 2017, 13:45 1 3,608 on 17/6/17
power loss in tuner ? Jul 17th 2016, 00:37 3 1,503 on 18/7/16
questions about AM broadcast band images Aug 24th 2015, 13:20 2 1,586 on 24/8/15
Use of old laptop power packs ? Dec 28th 2014, 15:30 1 2,019 on 28/12/14
Strange RFI on 10 meters and 6 meters Jun 19th 2014, 17:12 4 3,312 on 6/2/19
Two important functions missing in new radios ? Feb 4th 2013, 15:16 5 3,162 on 28/2/13

Latest Posts

Topic Author Posted On
Lets reach out to older hams in Nursing Homes N0HWJ on 3/7/20
I live in a suburb of Philadelphia, and agree that ham radio is a great hobby for seniors. Over the past few years, I've given a one-hour talk / demo about ham radio to several groups of seniors. I also contacted a local veterans home about this, as well as a huge nearby senior living facility. And I wrote a dozen or so licensed hams in assisted living facilities.

I was focused on showing how people with only an easily-obtained entry level license could use very cheap equipment such as an HT to communicate with other locals via the many repeaters in my area.

Although I received a lot of positive comments about this, nobody was interested enough to take the next step, much to my dismay.

I remain convinced that our seniors would benefit from ham radio, and that getting them on repeaters would be a good first step. But I wish I knew how to make it happen.

Be well.

73 de Allan, AB3FN
question about interference on 70 cm band AB3FN on 11/2/20
Its well-known that we are secondary users of the 70 cm band, but Part 97 only refers to interference to / from other specific services, e.g. mobile service near certain cities. What about other users of this portion of the spectrum?

For example, the medical procedure capsule endoscopy routinely uses frequencies around 430 MHz, albeit with power in the microwatt or milliwatt range. The likelihood of those devices creating interference to a ham is pretty small, but the likelihood of us creating interference to those devices is obviously much larger.

I cannot imagine any ham knowingly interfering with any medical procedure, but do FCC regulations, whether in Part 97 or elsewhere, address this?

Thanks in advance for your comments and clarification.
Function Generators WA4PMA on 7/1/20
I agree with Zak that a function generator has limited use in ham radio. But if somebody wants to tinker and experiment, its nice to have a variety of signal sources available. There are several extremely cheap function generator kits that will serve the average tinkerer well. A quick on-line search finds some that are in the $10-$20 range, and as a bonus these small kits are also fun to build.
calculation of PEP ? AB3FN on 21/3/19
Thanks, Zak, but I still don't grasp this.

Let's suppose that the modulating signal was not speech, but a constant amplitude single tone. The SSB waveform would be a clean sine. Would we still use the RMS value to calculate PEP ? I understand that average envelope power may generally be a more useful figure for us, so perhaps calling it peak envelope power is just a misnomer ? And if we're designing a circuit to handle true peak power, regardless of the waveform or duty cycle, then shouldn't we be concerned with the true peak voltage ? For signals other than speech modulated SSB, e.g. FM, is PEP normally calculated from true PEV or RMS ?

My apologies for belaboring this, but thanks in advance for the education.
calculation of PEP ? AB3FN on 20/3/19
I'm missing something basic here, and hope somebody can educate me.

Consider a typical SSB speech waveform. If we have PEV (peak envelope voltage) and want to calculate PEP (peak envelope power), we first convert the PEV into an RMS value. Then the RMS value is squared and divided by R to get PEP. So PEP really refers to the average power, and not to the true peak power.

Is this simply a peculiarity with terminology, or am I missing something fundamental about the calculation?

A quick search finds references to PEP calculations based on both the PEV and on the RMS value. Both cannot be correct.

Thanks in advance for your response.

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