Clifton Laboratories 7236 Clifton Road  Clifton VA 20124 tel: (703) 830 0368 fax: (703) 830 0711

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January 2010 Archive

 

28 January 2010

I've replaced a couple of photographs on the HP 59307A re-lamping page with higher quality versions, and added a photo of all the parts that must be removed to replace the lamps.

 

27 January 2010

I've added a new page illustrating a pet peeve of mine - equipment designs requiring a great deal of mechanical work to accomplish what would otherwise be a trivial job. In this case, the task is changing instrument lamps in an HP 59307A VHF switch, which should not be a job requiring major dismantling of  the unit, but in fact it does. To read the page, click here.

I'll have an update on the active antenna project tomorrow or the next day.

 

27 January 2010

The problem with blogpolls seems to have been resolved, and the poll is displayed reliably again.

I have updated the Z10040B manual to version 1.5, dated 27 January 2010, and uploaded it to my documents page. (Click here to read the new manual. It's nearly 5 MB long.) The manual has the same file name as the prior version, so all links should point to the new document. The changes incorporate the material of Service Bulletin 01.

I've also updated the Z10020 AM Medium Wave Band-Reject filter page to reflect the three design options (varying cutoff frequencies) now available, as well as a detailed performance analysis of a recent Z10020 filter built for Warren, K2ORS (who has consented to adding the document to my web page.) Warren's filter is a NDB/NAVTEX version with the lower -3 dB frequency moved upward to approximately 530 KHz.

 

25 January 2010

My new kit construction poll is not visible as of the evening of January 25th. The poll widget is from blogpolls.com and my site just links to their host computer to create the poll, keep track of the results, etc. It seems that the blogpolls.com server is down, or they've  gone out of business. (Note the service is blogpolls.com, not the similarly named blogpoll.com.)

 

23 January 2010

Added Naval Electronics VPA-30 active antenna to the 14 January 2010 table. I have not found the price for the VPA-30, however.

 

23 January 2010

A reader from France has identified an active antenna with performance specifications not in the 14 January 2010  table, the WiNRadio AX-81S. (Available in the US from Grove Enterprises, and others). I've added it to the table.

I'll add other active antennas available assembled or as kits as they are identified, providing measured performance data of IP2 and IP3 (or at least one of these figures) is available. I will not include antennas without performance data as it renders comparisons impossible.

 

21 January 2010

My active antenna printed circuit boards arrived today and I hope to build samples tomorrow or Saturday. In the "the best is the enemy of the good" category, the question is always when to stop refinement. It's a difficult decision and I like to provide kits that are as good as I know how to make it.

 

21 January 2010

As of 21 January 2010, I've added Service Bulletin No. 1 for the Z10040B covering potential instability where 2N5109s with unusually high UHF gain are used. This modification should not be necessary for any Z10040 amplifiers built or received as it is something I identified while building an amplifier with a new lot of 2N5109 transistors of exceptionally high UHF gain and all kits or assembled amplifiers using 2N5109s from this batch have the modification.

However, it is possible that a Z10040 may require replacement transistors due to component failure in the future, so I have documented the fix in this service bulletin. All new kits and assembled units after mid-January 2010 will include the modification as a preventative measure. Any Z10040A or B owners wish to make the modification should send an E-mail to me and I will provide the two 10pF disc ceramic capacitors. I will also update the Z10040B's Assembly Manual to reflect this change within the next few days.

 

15 January 2010

By popular demand, I've added data for no longer in production active antennas to the 14 January 2010  table.

 

15 January 2010

I've added two more Wellbrook loop antennas to the table of active antenna IP2/3 under January 14th's entry.

To keep the list meaningful, I've restricted it to (a) antennas that are currently available and (b) that have published IP2/IP3 specifications. I've made two exceptions to (b) because both are reasonably well known products.

 

15 January 2010

I've modified the table of active antenna IP2/IP3 values to add three antennas as suggested by a reader. Two of the three, however, do not have published intermodulation performance numbers that I've found.

To answer another question I've received, the Z1501 active antenna provide coverage of the 20 KHz - 30 MHz range. It may be used down to 10 KHz and up to 100 MHz with reduced performance.

 

14 January 2010

After more optimization work on the active antenna design over the last several weeks, I've settled on the required changes. I have ordered a couple dozen printed circuit  boards for two variant designs of the active antenna. I'll decide which variant is the best after building a couple of each type when the boards arrive, which should be around the end of next week or early the following week.

Both variants have performance, with 13.8V DC power, in the range of +84 dBm OIP2, +37 dBm OIP3. OIP2 is the 2nd order intercept (output referenced) and OIP3 is the 3rd order intercept (output referenced).

The table below shows how the Z1501 stacks up against the AMRAD designed antenna and commercially available active antennas. The table excludes antennas described in the literature, but not readily available as a kit or assembled.

I'm still working on pricing, but a Z1501 assembled, with a Z1203A DC power coupler will be cheaper than the DX Engineering antenna, let alone the other high performance antennas, and a kit will be significantly below the assembled price.

I might mention that several of these antennas are not user repairable as the electronics are potted in epoxy and no service information is provided. The Z1501 will have the usual detailed Clifton Laboratories assembly and operations manual, with full service information. All electronic parts are off-the-shelf and readily available. (In the electronics industry, it seems that "readily available" today means discontinued tomorrow, but that's something I have no control over.)

Manufacturer Model OIP2 (dBm) OIP3 (dBm) Price
Clifton Laboratories Z1501 >+80 dBm +37 to +38 dBm TBD
AMRAD Active LF Antenna +53 dBm +37 dBm N/A
DX Engineering DXE-ARAV2-1P Not specified +30 dBm $289.95
RF Systems DX One Pro MK II +80 dBm +52 dBm $799.75
RF Systems DX 10 +70 dBm +40 dBm $449.95
Dressler ARA 60 Not specified +50 dBm $349.95
Dressler ARA 100HDX Not specified +55 dBm $549.95
WiNRadio AX-81S +60 dBm +30 dBm $189.955
MFJ MFJ-1024 Not specified Not specified $159.95
LF Engineering HF-800 Not specified Not specified $149.00
Wellbrook ALA 1530PE North American* +70 dBm +40 dBm $276.11
Wellbrook ALA=1530+1 +75 dBm +41 dBm $309.91
Wellbrook ALA=1530S+1 +80 dBm +43 dBm $391.46
Datong AD-3702 +66/+46 dBm3 +36/+27 dBm3 N/A
Naval Electronics VPA 30 +60 dBm +38 dBm Unknown
McKay Dymek DA-1002 Not specified  +23 to +25 dBm4 N/A

Notes
1
Loop antenna. All others are electric field active antennas.
2 No longer in production. For historical reference only.
3 Figures are in form preamplifier out / preamplifier in
4Estimated, based on 1 dB compression point
5 DC power supply and coupler not included in price

In many circumstances, the 2nd order intercept point is more important than the 3rd order. In particular, much of the "crud" that can be heard between 1800 KHz and 3400 KHz is 2nd order intermodulation from AM broadcast stations. (Second order products are located at the sum and difference between two signals. For example, two AM broadcast stations at 760 KHz and 1500 KHz have second order intermodulation products at 1500-760 KHz = 740 KHz and 1500 + 760 KHz = 2260 KHz.)

Assuming I didn't blunder in the revised PCB layouts, the Z1501 active antenna should be ready for sale around the first of February.

I should add that if my objective was to offer only an assembled antenna, the design, optimization and re-design process would have taken much less time. It's difficult to develop a product that can be built and adjusted for optimum performance without sophisticated test equipment. I think I've solved that problem with a couple of alternative arrangements. In the worst case, critical parts of the antenna will be supplied assembled and adjusted. I think a process requiring only a decent digital voltmeter will work, but I can't be sure of that until I build a few of the new units and correlate DC measurements against measured IP2/IP3 data.

 

Part of the optimization work - a new front end hand wired prototype is grafted onto the output stage of the current Z1501 printed circuit board.
 
08 January 2010

As of 08 January 2010, it appears that LORAN-C will be decommissioned in the United States, possibly beginning as early as February, with all stations of the air by the end of the Federal Government's Fiscal Year, 01 October 2010.

I've accordingly added a page with views of LORAN-C signals as seen in frequency and time domain mode here in Clifton. I'll try to get a detailed view of an individual pulse over the next few days and add it to the page. To view the LORAN-C page, click here.

 

06 January 2010

I've spent most of the last two weeks working on improvements to the Z1501C active antenna. As a benchmark for the Z1501C's performance, I've used the AMRAD active antenna described in September, 2001 QST. The Z1501C at least meets the performance levels of the AMRAD design in both 2nd and 3rd order intermodulation, and is considerably better in input capacitance (lower capacitance translates to higher efficiency and increased signal level for the same ambient field strength).

However, Steve, AA7U, has suggested some changes in the Z1501C's design that will significantly improve 2nd order intermodulation performance, by 20 dB or more.This improvement is worth making. Unfortunately, the PCB layout must be revised for this change, which will add a couple weeks delay. I'll finish the PCB changes and enter an order in the next few days.

Still, the existing Z1501C prototype in my back yard works well. The spectrum analyzer plot below shows the 19.8 KHz VLF station NWC in Western Australia is around 10 dB above the noise level at 0730 this morning. The heavy black line is the average of 45 spectrum analyzer sweeps, and the thin olive color line is a single sweep. Averaging the sweeps markedly improves the signal to noise ratio.

NPM at 21.4 KHz in Pearl Harbor, HI is nearly 20 dB above the noise floor.
WWVB at 60 KHz uses amplitude shift keying to transmit a binary time code, with 17 dB reduction, with a bit rate of 1 bit/second. The image below is a "zero span" spectrum analyzer view of WWVB's signal in Clifton VA late yesterday evening. A spectrum analyzer operated in zero span means it acts like a traditional receiver, steady on one frequency, with the output showing signal level against time. The sweep time is 10 seconds, so each bit corresponds to one graticule width. Of course, the bit  transitions are not synchronized to the sweep, so the transitions won't align with the graticule lines.
 
01 January 2010

As usual, I've moved last month's entries to an archive page, reachable by clicking here or by the archive links at the top of this page.

In late October, I asked a question of my readers and potential customers on their construction preferences for new kits and to respond by E-mail. I've kept the "push button" poll using a service from www.blogpolls.com asking the question in this month's updates as well..  

I've added a new page, with a 1960's era neon lamp relaxation oscillator. I first built one around 1960 as part of a vacuum tube code practice oscillator to use when studying for my first amateur radio license.